True? CNN says lower octane on high octane-recommended doesn't hurt mileage.

[Throckmorton]

Doesn't it cause more wear on the engine? It's not like retarding timing cures AIDS and causes Hillary Clinton to withdraw from the primaries.

 

[GoingUp]

Skoorbie, I know your minivan is on DUBs and all, but you don't need premium in it

 

[Dunbar]

I don't understand why people can't uderstand this, I guess the oil companies advertising is really working. I also don't know why manufacturer's recomend premium in anything other than forced induction and high compression engines. Car and Driver tested this several years ago and found out that premium does make a difference in power with FI and high compression engines. But even a turbocharged car will drive absolutely fine on 87, I wouldn't recommend it for the race track though. BMW recommends 91 for 330 but I run exclusively 87 and there are no problems.

http://www.caranddriver.com/fe...lar_or_premium_feature

 

[Zenmervolt]

Originally posted by: Apex

Originally posted by: Zenmervolt

Originally posted by: vi edit
My Passat (2.8L V6) always seemed to get about 10% better milage with premium (recommended) vs. regular. So the cost difference was a wash.

But looking back on it now, I think that was around the same time that ethanol really started being added to regular blends and any vehicle I've ever owned has taken a 10% hit in milage with ethanol. So it was probably more of a factor of that than anything.

I don't think that premium fuels were ethanol "enhanced" at that time, nor are many right now. It's the low & mid grades that are tainted with it.

Since Ethanol raises octane rating, I'm actually surprised it's not the other way around.

The methods used to reduce knock will reduce the efficiency with which fuel is burned. Now, on a cool day with only one person in the car and driving down a flat interstate there probably won't be a difference because the engine would be retarding timing in that scenario. Put 4 people in the car, load it with luggage, and drive it up a mountain in the middle of August and you'll notice a definite lack of power as the engine management software pulls back timing by a huge amount to prevent detonation.

Of course, when people notice the bit of extra power from higher octane, they tend to use it, which means they drive less efficiently and may not see a mileage gain.

ZV

Ethanol has a lower BTU content than gasoline, thus the lower fuel efficiency.

I know that. I meant I was surprised that they were putting ethanol in the 87 octane and not the 91-93 octane since it's a subsidized way of increasing octane.

ZV

 

[Zenmervolt]

Originally posted by: Dunbar
I don't understand why people can't uderstand this, I guess the oil companies advertising is really working. I also don't know why manufacturer's recomend premium in anything other than forced induction and high compression engines. Car and Driver tested this several years ago and found out that premium does make a difference in power with FI and high compression engines. But even a turbocharged car will drive absolutely fine on 87, I wouldn't recommend it for the race track though. BMW recommends 91 for 330 but I run exclusively 87 and there are no problems.

http://www.caranddriver.com/fe...lar_or_premium_feature

There won't be problems. No-one is claiming there will be "problems". But you lose power, and reduce fuel efficiency for a given set of driving habits (many people react to the difference in power by altering driving habits and increase fuel economy because they aren't driving as hard as they used to) in order to save $200 or so each year on a car that cost you how much? Yes, you can make the argument that "every $200 counts", but that's illogical since if every $200 really did count, you wouldn't have a BMW. Based on pure logic, it just doesn't hold up.

Yes, even a modern turbocharged car will run OK on 87 (I'd burn a piston trying it on my '86 951 though since it can't dial down boost), but the ECU has to dial back boost as well as retarding timing and this results in significant power loss. For example, my 951 needs at least 92 octane and dynos 275 hp/300 tq at the rear wheels. If I were to dial it down to run on 87 without detonation I would lose around 75-100 hp (I've tested this).

ZV

 

[Nutdotnet]

Originally posted by: Zenmervolt

Originally posted by: Dunbar
I don't understand why people can't uderstand this, I guess the oil companies advertising is really working. I also don't know why manufacturer's recomend premium in anything other than forced induction and high compression engines. Car and Driver tested this several years ago and found out that premium does make a difference in power with FI and high compression engines. But even a turbocharged car will drive absolutely fine on 87, I wouldn't recommend it for the race track though. BMW recommends 91 for 330 but I run exclusively 87 and there are no problems.

http://www.caranddriver.com/fe...lar_or_premium_feature

There won't be problems. No-one is claiming there will be "problems". But you lose power, and reduce fuel efficiency for a given set of driving habits (many people react to the difference in power by altering driving habits and increase fuel economy because they aren't driving as hard as they used to) in order to save $200 or so each year on a car that cost you how much? Yes, you can make the argument that "every $200 counts", but that's illogical since if every $200 really did count, you wouldn't have a BMW. Based on pure logic, it just doesn't hold up.

Yes, even a modern turbocharged car will run OK on 87 (I'd burn a piston trying it on my '86 951 though since it can't dial down boost), but the ECU has to dial back boost as well as retarding timing and this results in significant power loss. For example, my 951 needs at least 92 octane and dynos 275 hp/300 tq at the rear wheels. If I were to dial it down to run on 87 without detonation I would lose around 75-100 hp (I've tested this).

ZV

Exactly. Well, close. Even though modern ECUs can retard timing to prevent knock, under certain variables, knocking can still occur when the ECU can not retard timing enough to prevent it. It's happened to me when I had to put 87 octane in my Turbo'd-Jetta years ago as an emergency. Although this is definetly more the rarity than the norm.

However, and like the educated have been saying: The "cost-savings" in buying 87 usually washes out with the lowered fuel-effeciency. Like I said before, my N/A R32 CAN run on 87 but gets significantly better gas mileage on 91...it also gets more power. Makes zero sense to run 87.

 

[charrison]

My 2000 maxima recommend premium, but is supposed to run regular. It started knocking after about 50k miles. So for the last 100k it has been premium only. That works out to be an 8% more at the pump. Not too big of a deal.

 

[The Boston Dangler]

i will continue to use premium. why risk my car's performance and health to save $1.80 off of $72?

 

[LTC8K6]

I see people buy $6 bottles of octane booster to add to their tank of regular and boost it 1 or 2 points...

Makes no sense at all.

A tank of 89 or even 93 octane would cost them less.

 

[Colt45]

Originally posted by: Nutdotnet

Originally posted by: Zenmervolt

Originally posted by: Dunbar
I don't understand why people can't uderstand this, I guess the oil companies advertising is really working. I also don't know why manufacturer's recomend premium in anything other than forced induction and high compression engines. Car and Driver tested this several years ago and found out that premium does make a difference in power with FI and high compression engines. But even a turbocharged car will drive absolutely fine on 87, I wouldn't recommend it for the race track though. BMW recommends 91 for 330 but I run exclusively 87 and there are no problems.

http://www.caranddriver.com/fe...lar_or_premium_feature

There won't be problems. No-one is claiming there will be "problems". But you lose power, and reduce fuel efficiency for a given set of driving habits (many people react to the difference in power by altering driving habits and increase fuel economy because they aren't driving as hard as they used to) in order to save $200 or so each year on a car that cost you how much? Yes, you can make the argument that "every $200 counts", but that's illogical since if every $200 really did count, you wouldn't have a BMW. Based on pure logic, it just doesn't hold up.

Yes, even a modern turbocharged car will run OK on 87 (I'd burn a piston trying it on my '86 951 though since it can't dial down boost), but the ECU has to dial back boost as well as retarding timing and this results in significant power loss. For example, my 951 needs at least 92 octane and dynos 275 hp/300 tq at the rear wheels. If I were to dial it down to run on 87 without detonation I would lose around 75-100 hp (I've tested this).

ZV

Exactly. Well, close. Even though modern ECUs can retard timing to prevent knock, under certain variables, knocking can still occur when the ECU can not retard timing enough to prevent it. It's happened to me when I had to put 87 octane in my Turbo'd-Jetta years ago as an emergency. Although this is definetly more the rarity than the norm.

Yep, my car can only dial it back a little bit, if it's still pinging after that, it throws the check engine light. ( 8 degrees max, iirc )

My car is an antique though, it still has a distributor. New cars with coilpacks should be able to arbitrarily retard the timing as much as they'd like...

Can't turn down the boost either, but that's my fault
So I tend to go light on the pedal when I'm stuck out in the boondocks and have to get 87.

 

[StageLeft]

Originally posted by: Vic
I just looked up the CNN article in question text and was interested to note that it has now been edited and a disclaimer added:
"-Editors note: This story was revised from an earlier version to clarify that the advice to use regular gas instead of premium may not apply to all cars."

Hehe, nice catch, thanks.

Skoorbie, I know your minivan is on DUBs and all, but you don't need premium in it

Minivan needs 95 or knocks like mad. I have it running hella high compression, but it is pulling the quarter like balls!

 

[Capt Caveman]

Driving cross-country, I noticed that I'd lose 2 mpg if I didn't use premium.

 

[Throckmorton]

Originally posted by: The Boston Dangler
i will continue to use premium. why risk my car's performance and health to save $1.80 off of $72?

People are dumb, and CNN is irresponsible for encouraging them

 

[BarneyFife]

The difference between regular and premium for 12k miles a year is around $120.

I know some people that do that to save money. Its $120 for a freaking year.

 

[Dunbar]

Originally posted by: Zenmervolt
There won't be problems. No-one is claiming there will be "problems". But you lose power, and reduce fuel efficiency for a given set of driving habits (many people react to the difference in power by altering driving habits and increase fuel economy because they aren't driving as hard as they used to) in order to save $200 or so each year on a car that cost you how much?

I'm not suggesting people with forced induction run 87, just pointing out that even in that extreme example the car will drive just fine. If you have a NA car running less than 11:1 compression it's a waste of money to buy premium. As the article points out it won't give you more power and I don't buy that it will change MPG one bit (there's no scientific basis for it.) It's not a money issue, there is just no good reason for 95% of cars to run anything but 87 octane. There's a lot of misinformation and just plain ignorance when it comes to this subject.

 

[Nutdotnet]

Originally posted by: Dunbar

Originally posted by: Zenmervolt
There won't be problems. No-one is claiming there will be "problems". But you lose power, and reduce fuel efficiency for a given set of driving habits (many people react to the difference in power by altering driving habits and increase fuel economy because they aren't driving as hard as they used to) in order to save $200 or so each year on a car that cost you how much?

I'm not suggesting people with forced induction run 87, just pointing out that even in that extreme example the car will drive just fine. If you have a NA car running less than 11:1 compression it's a waste of money to buy premium. As the article points out it won't give you more power and I don't buy that it will change MPG one bit (there's no scientific basis for it.) It's not a money issue, there is just no good reason for 95% of cars to run anything but 87 octane. There's a lot of misinformation and just plain ignorance when it comes to this subject.

You mean your ignorance???

Here...I'll pull up a great example on how a vehicle that is supposed to run 91 octane gets better MPG at 91 octane vs. 87. On a NA engine no less...just give me a few.

 

[TheSlamma]

Originally posted by: Colt45

Originally posted by: Nutdotnet

Originally posted by: Zenmervolt

Originally posted by: Dunbar
I don't understand why people can't uderstand this, I guess the oil companies advertising is really working. I also don't know why manufacturer's recomend premium in anything other than forced induction and high compression engines. Car and Driver tested this several years ago and found out that premium does make a difference in power with FI and high compression engines. But even a turbocharged car will drive absolutely fine on 87, I wouldn't recommend it for the race track though. BMW recommends 91 for 330 but I run exclusively 87 and there are no problems.

http://www.caranddriver.com/fe...lar_or_premium_feature

There won't be problems. No-one is claiming there will be "problems". But you lose power, and reduce fuel efficiency for a given set of driving habits (many people react to the difference in power by altering driving habits and increase fuel economy because they aren't driving as hard as they used to) in order to save $200 or so each year on a car that cost you how much? Yes, you can make the argument that "every $200 counts", but that's illogical since if every $200 really did count, you wouldn't have a BMW. Based on pure logic, it just doesn't hold up.

Yes, even a modern turbocharged car will run OK on 87 (I'd burn a piston trying it on my '86 951 though since it can't dial down boost), but the ECU has to dial back boost as well as retarding timing and this results in significant power loss. For example, my 951 needs at least 92 octane and dynos 275 hp/300 tq at the rear wheels. If I were to dial it down to run on 87 without detonation I would lose around 75-100 hp (I've tested this).

ZV

Exactly. Well, close. Even though modern ECUs can retard timing to prevent knock, under certain variables, knocking can still occur when the ECU can not retard timing enough to prevent it. It's happened to me when I had to put 87 octane in my Turbo'd-Jetta years ago as an emergency. Although this is definetly more the rarity than the norm.

Yep, my car can only dial it back a little bit, if it's still pinging after that, it throws the check engine light. ( 8 degrees max, iirc )

My car is an antique though, it still has a distributor. New cars with coilpacks should be able to arbitrarily retard the timing as much as they'd like...

Can't turn down the boost either, but that's my fault
So I tend to go light on the pedal when I'm stuck out in the boondocks and have to get 87.

You guys need to the right tools and learn to do your own PCM programming then.

After I added an aftermarket suprcharger and 40lb injectors I found it to be a need to program my own PCM. That way you can change your timing/fuel tables and range of retard the knock sensor can trigger.

My vehicle (and many others) has 2 tables.. the more advanced timing at startup and one for when knock has been detected. I have ran on my current timing/fuel tables for 2 years now and havent had to touch them when I use 91 or 87 oct (High altitude octaine levels)

 

[Jeff7181]

If memory serves me... modern engines will lean out the air/fuel mixture in addition to the usual timing adjustments at cruising speeds until knocking is detected. Ratios can get as high as 16 or 17 to 1 under these conditions. An engine designed for high octane fuel will no doubt experience knock at lower air/fuel ratios as a rich mixture is less prone to knocking than a lean mixture. The result is an engine that uses less fuel when cruising.

The guys on one of those weekend automotive shows on Speed did a test once with either a ZZ4 or 502 Crate engine, can't remember which. Anyhow... the result was that more power and better fuel efficiency was obtained with high octane fuel than with regular.

In short... I have to call BS on CNN until they provide actual numbers since what they say is contrary to what I've learned in my schooling and test results I've seen.

 

[Zenmervolt]

Originally posted by: Dunbar
I don't buy that it will change MPG one bit (there's no scientific basis for it.)

Pray tell then, what does retarding timing and enriching the fuel mixture (the two steps taken by modern ECUs to deal with detonation caused by low-octane fuel) do?

Oh, right, decrease power and decrease efficiency. That's scientific fact. You are welcome to disbelieve but that won't make you right.

ZV

 

[DivideBYZero]

Scoorb effect.

 

[Nutdotnet]

Here's my follow-up to the 87 vs. 91 thread.

Read the initial post:

LINK

 

[LTC8K6]

Yeah but there are tests like that all over the net and the results are all over the place.

 

[randomlinh]

Originally posted by: The Boston Dangler
i will continue to use premium. why risk my car's performance and health to save $1.80 off of $72?

Given the average spread of 30 cents between regular and premium here, that means you paid ~$12/gal?

But yes, I understand your point.

Also, there's no risk really for modern engines (altho, I still wouldn't go below 91 for FI). It's just a matter of why the hell would I want to lose performance... that was the whole reason I paid for a high end car.

As for the R32 test... two days of data doesn't really prove anything. Not to discount the theory, but just saying.

The bottom line is if premium is hurting your budget, you should be looking at a totally different car.

 

[Throckmorton]

By the way, how do you think the engine knows to retard timing unless it knocks first? Why would you do that to your engine?

 

[Nutdotnet]

Originally posted by: randomlinh

Originally posted by: The Boston Dangler
i will continue to use premium. why risk my car's performance and health to save $1.80 off of $72?

Given the average spread of 30 cents between regular and premium here, that means you paid ~$12/gal?

But yes, I understand your point.

Also, there's no risk really for modern engines (altho, I still wouldn't go below 91 for FI). It's just a matter of why the hell would I want to lose performance... that was the whole reason I paid for a high end car.

As for the R32 test... two days of data doesn't really prove anything. Not to discount the theory, but just saying.

The bottom line is if premium is hurting your budget, you should be looking at a totally different car.

I'd agree...two days doesn't prove MUCH but it does help show that there is a difference in 87 vs. 91 in certain vehicles.

And I'd agree with you on if premium is hurting your budget then you REALLY should not be buying this type of vehicle.