Cars that "require" premium gasoline

[Chunkee]

Any of you guys have these cars and put just regular gas in them from time to time? Any realized detriment?

These are the cars I am looking at on the fun side.

Thank you.

jC

 

[Howard]

Yeah, I use unleaded all the time.

EDIT: Uh, regular. Civic Si.

 

[sniperruff]

i think the anti-knock sensor will change the engine's timing so it won't knock even if you use regular on a premium-only engine. with that said, the lowest grade i've put in my VQ35 was plus, but whatever, it's only like $2 more per fill-up.

 

[996GT2]

The TL and Si both use high-compression (11.0:1) engines that run better off premium fuel. The GTI and MS3 both use turbocharged engines, so premium fuel is necessary to prevent detonation. You CAN use regular fuel in most modern engines even if they "require" premium, but the trade-off is reduced power and fuel economy due to changes made by the ECU when it detects that a lower octane fuel is being used. In the end, the reduced MPG probably means that you end up paying the same amount to go a given distance. Besides, it's only a few dollars more per fill up to use premium, so why not just follow the manufacturer's guidelines?

 

[fstime]

Your going to loose performance and gas miliage so its pointless.

It wont do any harm if you try it a couple times, engine timing will adjust, I wouldnt make a habit of it though.

 

[zerocool84]

Originally posted by: BouZouki
Your going to loose performance and gas miliage so its pointless.

It wont do any harm if you try it a couple times, engine timing will adjust, I wouldnt make a habit of it though.

Yea seriously what's the point. Your losing gas mileage and performance for saving like a dollar or two at the pump. No reason whatsoever. My car requires premium and I have never put in regular.....well I accidentally did put in 2 gallons of regular.

 

[compman25]

My WRX has sometimes gotten 87 on accident. No harm done.

 

[Arkaign]

Originally posted by: zerocool84

Originally posted by: BouZouki
Your going to loose performance and gas miliage so its pointless.

It wont do any harm if you try it a couple times, engine timing will adjust, I wouldnt make a habit of it though.

Yea seriously what's the point. Your losing gas mileage and performance for saving like a dollar or two at the pump. No reason whatsoever. My car requires premium and I have never put in regular.....well I accidentally did put in 2 gallons of regular.

x2

The weaker performance/efficiency washes the savings in the end. Though as noted, it won't cause any damage with occassional/moderate 87/89 in the tank.

 

[Scouzer]

My 2.4L G5 GT recommends Premium in the manual. I was a firm believer I could get away with 87, but I noticed I had an annoying starting problem. Put in premium for a couple tanks, problem goes away.

Also, I'm not sure if it was knock or ping or what... but at very high RPM, it sounded like metallic diarrhea with 87, sounds fine with 89 or 91.

Contrary to popular opinion though, I get better fuel economy with 87.

 

[mwmorph]

87 has slightly more energy content because theres more hydrocarbons to be burned and fewer octane boosting additives so MPG could go up on 87, but for a car absolutely tuned for 91, it could also go down, depends on the vehicle.

As for running 87, on a normal engine, it's not too bad, you'll lose some power but it won't be too dramatic, you'll feel it and it'll suck but it wont be anything compared to some turbo or supercharged engines. Higher boost engines like the Acura RDX and Mazdaspeed3 can lost A LOT of power by going down to 87 because boost will be cut.

Friend's wife had an RDX and accidentally filled a tank with 87 and it basically had zero pickup and no power, felt like she was driving a slightly mobile, extremely underpowered roadblock.

 

[summit]

I went to a gas station twice and filled up accidentally with 89 instead of 91 because im used to the 91 pump being on the far right and not middle. Both times I noticed significant poorer gas mileage.

 

[mwmorph]

Originally posted by: Summit
I went to a gas station twice and filled up accidentally with 89 instead of 91 because im used to the 91 pump being on the far right and not middle. Both times I noticed significant poorer gas mileage.

Makes sense, on a naturally aspirated engine you're mainly going to be retarding the timing, decreasing power and thus requiring more throttle input for the level of acceleration you're used. More RPMs always means more gas burned.

Also on direct injected in particular gasoline at high pressure essentially vaporizes in the combustion chamber, cooling the intake charge and reducing overall temperature as is done in the DISI MZR (Mazdaspeed 3) engine and thus running rich will result in a cooler engine (in both normal fuel injected and direct injected models cools the engine, though it affects Direct Injected cars a bit more) and thus prevent preignition. Spraying more fuel per cylinder of course will decrease your mileage and unburned fuel heats up your catalytic converter quicker and to a higher temperature which is not a good thing as those tend to be a bit expensive.

Catalytic converters don't function until around 400-600 degrees f and optimal temp is 1400-1600 degrees but if you go too far beyond that, the results are nothing but detrimental. At 2000 degrees the Al-oxide honeycomb structure weakens and the platinum/palladium plating starts to melt. As a general rule of thumb, anything that is melting on a car is usually very, very bad.

I can't give specifics on how much more your catalytic converter heats up and it most likely wont melt on your car, but running rich all the time will break it down more quickly and running 87 in a 89, 91 or 93 engine will force it to run rich.

The good news is that emissions control warranties tend to be very long and cover a lot of miles and OEM catalytic converters are designed to go well over 100K miles.

 

[DivideBYZero]

Engines run cooler when running rich, not hotter, AFAIK.

 

[CptCrunch]

1998 dodge dakota, runs like sh*t on 87, on 89 it runs great, and gets an extra 2mpg

 

[Gand1]

2000 Audi TT. Wife put 87 in once "cause she didn't know" and it ran like shit. 93 octane only.

 

[Capt Caveman]

Driving cross-country in my QX4, I got 2 mpg less using regular instead of premium.

 

[Rio Rebel]

My wife drives an Acura TL (base model), and she puts plus in it all the time (89 octane). I've told her over and over that she's not saving anything by doing that, but she ignores me. She claims to get the same mileage and can't tell the difference.

I tried putting regular once in my TL-S, and I believed I felt a noticeable loss of power. I didn't notice a difference in mpg (but didn't track it all that closely). After that one tank, I have put nothing but premium in it.

I have heard a lot of discussion on this, and there seems to be varying opinions on the effect it could have on your engine. It seems to be almost universally agreed, though, that you aren't really gaining anything by doing it and it makes more sense to stick to the manufacturer's guidelines.

 

[mwmorph]

Originally posted by: mwmorph

Originally posted by: Summit
I went to a gas station twice and filled up accidentally with 89 instead of 91 because im used to the 91 pump being on the far right and not middle. Both times I noticed significant poorer gas mileage.

Makes sense, on a naturally aspirated engine you're mainly going to be retarding the timing, decreasing power and thus requiring more throttle input for the level of acceleration you're used. More RPMs always means more gas burned.

Also on direct injected in particular gasoline at high pressure essentially vaporizes in the combustion chamber, cooling the intake charge and reducing overall temperature as is done in the DISI MZR (Mazdaspeed 3) engine and thus running rich will result in a cooler engine (in both normal fuel injected and direct injected models cools the engine, though it affects Direct Injected cars a bit more) and thus prevent preignition. Spraying more fuel per cylinder of course will decrease your mileage and unburned fuel heats up your catalytic converter quicker and to a higher temperature which is not a good thing as those tend to be a bit expensive.

Catalytic converters don't function until around 400-600 degrees f and optimal temp is 1400-1600 degrees but if you go too far beyond that, the results are nothing but detrimental. At 2000 degrees the Al-oxide honeycomb structure weakens and the platinum/palladium plating starts to melt. As a general rule of thumb, anything that is melting on a car is usually very, very bad.

I can't give specifics on how much more your catalytic converter heats up and it most likely wont melt on your car, but running rich all the time will break it down more quickly and running 87 in a 89, 91 or 93 engine will force it to run rich.

The good news is that emissions control warranties tend to be very long and cover a lot of miles and OEM catalytic converters are designed to go well over 100K miles.

Originally posted by: DivideBYZero
Engines run cooler when running rich, not hotter, AFAIK.

They sure do, but catalytic converters, which are part of your emissions control system and exhaust, don't.

 

[krunchykrome]

Fiancee puts mid grade in her 2004 TSX, even though it "requires" premium. No problems at all.

Her parents put mid-grade in their Infiniti's as well, and no problems there either.

 

[Dr. Detroit]

After spending $20 - $35K on a car how exactly does 20 cents a gallon affect your budget?

On 15 gallons thats $3.00 a fill up and I'd rather stick to what the manufacturer intended for the car as I enjoy the performance that its tuned for.


'06 Saab 9-3 Aero

 

[Zenmervolt]

Originally posted by: krunchykrome
Fiancee puts mid grade in her 2004 TSX, even though it "requires" premium. No problems at all.

Her parents put mid-grade in their Infiniti's as well, and no problems there either.

As already mentioned in the thread, there will be no immediate drivability problems. However, mileage will be reduced (which entirely negates the negligible cost savings on the lower-octane fuel) and there are long term negative effects on the catalytic converter that will come into play at over 100,000 miles.

ZV

 

[Scouzer]

Originally posted by: Zenmervolt

Originally posted by: krunchykrome
Fiancee puts mid grade in her 2004 TSX, even though it "requires" premium. No problems at all.

Her parents put mid-grade in their Infiniti's as well, and no problems there either.

As already mentioned in the thread, there will be no immediate drivability problems. However, mileage may be reduced (which entirely negates the negligible cost savings on the lower-octane fuel) and there are long term negative effects on the catalytic converter that will come into play at over 100,000 miles.

ZV

fixed

 

[Zenmervolt]

Originally posted by: Scouzer

Originally posted by: Zenmervolt

Originally posted by: krunchykrome
Fiancee puts mid grade in her 2004 TSX, even though it "requires" premium. No problems at all.

Her parents put mid-grade in their Infiniti's as well, and no problems there either.

As already mentioned in the thread, there will be no immediate drivability problems. However, mileage WILL reduced (which entirely negates the negligible cost savings on the lower-octane fuel) and there are long term negative effects on the catalytic converter that will come into play at over 100,000 miles.

ZV

fixed

Fixed again. Sorry, but the measures taken to stop pre-ignition absolutely and unequivocally reduce fuel efficiency. Redtarding timing reduces fuel efficiency. Running richer to counter knock reduces fuel efficiency. You cannot change the laws of physics.

ZV

 

[amdhunter]

Originally posted by: Chunkee
Any of you guys have these cars and put just regular gas in them from time to time? Any realized detriment?

These are the cars I am looking at on the fun side.

Thank you.

jC

MY GLi requires premium. I haven't dared put in regular yet, but I might when I hit ~20-30k miles. It took me 7 months to put 2500 though. lol

 

[zerocool84]

Originally posted by: Fmr12B
After spending $20 - $35K on a car how exactly does 20 cents a gallon affect your budget?

On 15 gallons thats $3.00 a fill up and I'd rather stick to what the manufacturer intended for the car as I enjoy the performance that its tuned for.


'06 Saab 9-3 Aero

lol yep that's some funny stuff right there.