Premium gas vs. regular: What's really better for your car? (CBC Marketplace)

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SparkyJJO

Lifer
May 16, 2002
13,357
7
81
If it says to use premium, use premium.
If it says to use regular, use regular.

Not that hard. Why is this even a discussion?

If you don't want to use premium gas then don't buy a car that calls for it!
 

Mir96TA

Golden Member
Oct 21, 2002
1,949
37
91
They are lot other things to consider when you think about Short Terms Fuel tables, Long Terms fuel Tables........ etc.....
 

Brian Stirling

Diamond Member
Feb 7, 2010
4,000
2
0
Energy density is an entirely different topic than octane. If we're talking economy, then yes - gasoline is preferable. If we're talking power, E85 is up there (or better than) race gas.


Yes, it never fails to amaze me how many guys will spend thousands to increase engine power by 20hp and then brag about using 100% gasoline. Ethanol will lower mpg but increase power -- fact! Ethanol has about 1/3 less energy per gallon than gasoline so gas with 10% ethanol will tend to get about 3.4% lower mpg, but will provide a bit more power.


Brian
 

tortillasoup

Golden Member
Jan 12, 2011
1,977
3
81
EFI engines have had knock sensors since the mid-1980s. Perhaps not universally, but they've definitely been around at least that long. Engines with knock sensors detect knock (which is detonation, an entirely different thing than preignition, and definitely different from "predetonation" which is a nonexistent nonsense term that apparently conflates detonation and preignition) and adjust for it long before it's detectable by humans. Most engines simply adjust by pulling back timing when knock is detected - there's no need to read the octane of the fuel itself.

That said, if the engine says "premium required" that means the programming cannot pull back the timing enough to compensate for lower octane fuel in all situations and running anything less may cause detonation severe enough to cause damage under high-load situations.

ZV
Basically this... You CAN get away with a lower octane if you go to a higher altitude, colder temperatures and higher humidity. Also relying on knock sensors isn't always good because some cars like some Hondas had notoriously unreliable knock sensors that wouldn't detect some knock.
 

Art&Science

Senior member
Nov 28, 2014
339
4
46
EFI engines have had knock sensors since the mid-1980s. Perhaps not universally, but they've definitely been around at least that long. Engines with knock sensors detect knock (which is detonation, an entirely different thing than preignition, and definitely different from "predetonation" which is a nonexistent nonsense term that apparently conflates detonation and preignition) and adjust for it long before it's detectable by humans. Most engines simply adjust by pulling back timing when knock is detected - there's no need to read the octane of the fuel itself.

That said, if the engine says "premium required" that means the programming cannot pull back the timing enough to compensate for lower octane fuel in all situations and running anything less may cause detonation severe enough to cause damage under high-load situations.

ZV

Some cars have had knock sensors since the 1980s - most however, most have not. You can Google this stuff, you know. For your other points - you can argue semantics with yourself to your heart's content - it really doesn't affect me.
 

tortillasoup

Golden Member
Jan 12, 2011
1,977
3
81
Some cars have had knock sensors since the 1980s - most however, most have not. You can Google this stuff, you know. For your other points - you can argue semantics with yourself to your heart's content - it really doesn't affect me.

Well, ALL OBD-II cars must have knock sensors, that much is certain!
 

cabri

Diamond Member
Nov 3, 2012
3,616
1
81
Basically this... You CAN get away with a lower octane if you go to a higher altitude, colder temperatures and higher humidity. Also relying on knock sensors isn't always good because some cars like some Hondas had notoriously unreliable knock sensors that wouldn't detect some knock.

Flat landers usually have min octane at the pumps at 87

In the bumps of Colorado, 85 is normal.

When I fill up the tank at 87 in Nebraska/Kansas and use it in Colorado, I can notice the difference.
Conversely, when heading into Nebraska/Kansas, I will leave Colorado with only a half tank of fuel and fill up when I hit the areas that have 87 for the regular price.
 

Pacfanweb

Lifer
Jan 2, 2000
13,149
57
91
Some cars have had knock sensors since the 1980s - most however, most have not. You can Google this stuff, you know.

Let's see....since 1980, and it's 2015 now, right?

That's 35 years, and I'd say for sure that nearly all cars since 1990 have had knock sensors, and I know for a fact that some in the 80's did, too.

What part of that time frame do you think represents the most cars? 1980-90, or 1990-now?

So the statement "most cars have not had knock sensors since the 80's" is incorrect.

Ford went to EEC IV (which is now their version of OBD I) in 1984, and IIRC all their cars had it by 1988, and I'm almost certain all of them had knock sensors, at least the injected ones.
I'd say it's reasonable to assume that most other manufacturers followed roughly the same time table.

I'd say that for half the 80's, most cars had knock sensors, and since then all of them have.

So Zen was right on.
 
Last edited:

slag

Lifer
Dec 14, 2000
10,473
81
101
Both my vehicles are supercharged, so premium it is. Sadly, here in Kalifornia, "premium" is still only 91 octane. Apparently, we just can't have nice things.

My wife's vehicle is supercharged.. doesn't require premium..
Plenty of power with standard 87 octane with zero alcohol.
 

jlee

Lifer
Sep 12, 2001
48,513
221
106
My wife's vehicle is supercharged.. doesn't require premium..
Plenty of power with standard 87 octane with zero alcohol.

Ethanol is wholly irrelevant for power when we are talking about E10/87 or E0/87.
 

SearchMaster

Diamond Member
Jun 6, 2002
7,792
114
106
My car has Ford's 2.0EB, and it recommends premium but says it will have 5 less HP on 87 octane.

Where I live, premium is $0.30 more per gallon than 87 octane and I have no problem paying that. Occasionally on a road trip, I'll encounter as much as $0.60 more per gallon for premium, which is just outrageous IMO. Since I'm generally just driving at a flat 75MPH on those trips anyway, I'll often use 87 octane. MPG doesn't suffer noticeably.
 

cabri

Diamond Member
Nov 3, 2012
3,616
1
81
My wife's vehicle is supercharged.. doesn't require premium..
Plenty of power with standard 87 octane with zero alcohol.

Problem is finding fuel with zero alcohol/ethanol.

It can be done is most places, but it may take a drive to get to the station
 

996GT2

Diamond Member
Jun 23, 2005
5,212
0
76
Problem is finding fuel with zero alcohol/ethanol.

It can be done is most places, but it may take a drive to get to the station

/facepalm

Why facepalm? It is in fact very difficult to find ethanol-free gas in most places. For example there is only 1 place in my area which is listed on pure-gas.org and they apparently charge $5/gallon from the comments...
 

jlee

Lifer
Sep 12, 2001
48,513
221
106
Why facepalm? It is in fact very difficult to find ethanol-free gas in most places. For example there is only 1 place in my area which is listed on pure-gas.org and they apparently charge $5/gallon from the comments...

In a conversation about 87 vs 91/93, E0 vs E10 is irrelevant. The octane rating is the same.
 

exar333

Diamond Member
Feb 7, 2004
8,518
8
91
Why facepalm? It is in fact very difficult to find ethanol-free gas in most places. For example there is only 1 place in my area which is listed on pure-gas.org and they apparently charge $5/gallon from the comments...

Totally agree.

Especially with E15 rolling-out to replace E10 at a number of places...some engines really don't work the best with ethanol and I avoid it as well when able.
 

Ackmed

Diamond Member
Oct 1, 2003
8,478
524
126
Problem is finding fuel with zero alcohol/ethanol.

It can be done is most places, but it may take a drive to get to the station

It used to be around here, but there are more and more that have it. I have one that sells nothing but 100% gas, and several others that have at least one pump with it. Only two have 100% and 93 octane though, which is what I use. My daily driver is a built '68 Mustang though. I can tell a huge difference with 87 and 10%.. I did it once just to see. Every so often I put half a tank of racing fuel in it, but it's about $8 a gallon. Smells nice though when opening it up. For whatever reason there are more 100% pumps, and I like it.
 

Zivic

Diamond Member
Nov 25, 2002
3,505
38
91
Dyno it. Butt dyno doesn't count.

I had an 01 stratus R/T coupe. I saw 15% better fuel mileage on premium vs 87. it felt better as well, but the mileage was more than enough reason to pay the premium for 93
 

Ferzerp

Diamond Member
Oct 12, 1999
6,438
107
106
I had an 01 stratus R/T coupe. I saw 15% better fuel mileage on premium vs 87. it felt better as well, but the mileage was more than enough reason to pay the premium for 93

Mileage is a tricky thing to measure unless you specifically don't know what is in the tank. Mileage is so strongly tied to driving that even thinking about mileage gives you a marked improvement in mileage.
 

Auric

Diamond Member
Oct 11, 1999
9,596
2
71
But that's how it generally works: an engine designed for higher octane will consume more if given lower octane -ergo little to no "savings" while reducing performance. And really, even when fuel prices have been historically high, it still ranks by cost of ownership after depreciation, insurance, and maintenance. Furthermore, historically low prices generally coincide with economic recession and so are balanced by reduced "affordability". And in any case the bulk of the cost is not shown "at the pump" but rather in income tax, public debt, and other effects of maintaining global supply.
 

Ackmed

Diamond Member
Oct 1, 2003
8,478
524
126
Dyno it. Butt dyno doesn't count.

Not yet, not all the way done with it. Putting in a stale converter soon, port and polishing the heads, and a bigger cam. Perhaps one day.

I don't know my exact mileage, but it is pretty low. I've got an aftermarket dash that doesn't keep track if mileage very well, it's digital. It went way down after putting in my 4.11 gear. I can easily run out a tank in an afternoon of driving. But I also can't help but keep my foot off the gas, and have a 750 Holley double pumper 4 barrel carb.
 

nakedfrog

No Lifer
Apr 3, 2001
58,570
12,874
136
Mileage is a tricky thing to measure unless you specifically don't know what is in the tank. Mileage is so strongly tied to driving that even thinking about mileage gives you a marked improvement in mileage.
Well, around here at least, it's not uncommon for the regular and midgrade to be E-10 and the premium to have no ethanol.
 
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