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The Premium Fuel Better Mileage Controversy

47K views 126 replies 49 participants last post by  Merc6 
#1 ·
Ran 2 tanks each with both 91 and 87 just for trial and I get absolutely NO change in fuel mileage. At all. Slightly smoother performance with Premium, but nothing really to warrant the extra cost. I use Sunoco since its the only decently tiered gasoline near my home. However here in college I have access to both Exxon and Shell and switched to them since they are top tier. Either way, octane rating has caused no difference for me at all. Anyone's thoughts on this?
 
#40 ·
I'm getting ready to try 93 in a few days, where can I get gas that is 100% gas?! It always says at least 10% eth.
Cant really help you there, but around where I am at, most Kwik Trips have no eth on there premium, which is 91 oct. My station just so happens to have 87 and 91 no eth. Also around my area there are not that many stations with 93, but all of the ones I have seen that are 93 have 10% eth, where as most of the 91 have no eth.

For the people saying they would never run 87 and never trust the knock sensor, that is fine, I am sure you know much more than me, but these motors have come a long way from previous FI motors. And with the knock sensors they are pretty good, I agree they cant prevent everything but I know a husband and a wife from corvette forum that have a ls2 vette, which gm recommends 91 fuel but says less is ok if 91 is not available. Well they have have if i remember right over 60k miles and have allways used 87 oct and never had any problems. I do not do that on my vette and never would (unless I am in a bind, but I would put 89 in before 87)because you are not getting the full potential but the knock sensors obviously work, and the ls2 has a lot more compression than the 1.4, granted it is not FI. But if a motor will run that long on a motor that GM recommends 91 on, I think a motor (the 1.4) that GM says to run 87 on will do just fine. But again I am not a engineer or anything like that, just am good with common sense, and have no experience with FI,compared to the knowlege of some of the members here.
 
#41 ·
I'm not an automotive engineer, just a "shade-tree" mechanic type of guy, but my LTZ runs better on 93 vs the 87 (can't find 91 around here). I don't know the reason, and it may be psychological, but the car seems more peppy with the higher octane. Also according to the DIC, I average 34 mpg on the highway with 93 and 30 with the 87 over the same route.
 
#43 ·
...audog has your answer:

I'm not an automotive engineer, just a "shade-tree" mechanic type of guy, but my LTZ runs better on 93 vs the 87 (can't find 91 around here). I don't know the reason, and it may be psychological, but the car seems more peppy with the higher octane. Also according to the DIC, I average 34 mpg on the highway with 93 octane and 30 mpg with the 87 octane over the same route.
 
#44 ·
There is not always a difference in fuel mileage. There is no difference for me. It's mainly a performance and better for your engine type deal. Differences in mileage may be if your switching between different stations and brands, etc. The Sunoco I usually go to gives me the same mileage on 87, 91, and 93 and its been that way with my last vehicle too. But all grades of its gas seem to give me 2-3 mpg better than the no-name (aka big corp.) gas stations in the area.
 
#45 ·
Money wise, I always put $30, it lasts just under a week. So as my first 93 tank, I did $30 to see the difference in how long til I needed to fill up again. I usually get around 8.8x gallons each fill up with 87, I got 8.406 gallons with 93 octane. not bad.
 
#47 ·
I'm just about to finish my first FULL tank of 91 octane. So far, gas mileage has been about the same (more or less) as with 87. However, I believe i've had a little more stop and go traffic to contend with...so I'm sure my MPG's could have a bit better.

I did notice the car felt better though.
 
#49 ·
If you don't fill up at the same pump with the same technique every time when tracking fuel mileage, the results are tainted. They're good for rough changes, but not for tracking fine changes like 1-2 mpg difference over a commute.

One also needs about 3 tanks to really discern a change as fine as 1-2 mpg.
 
#51 ·
I don't claim to be any kind of expert but different octane levels won't make a difference in your MPG. If your gas stations are like the ones in my area running premium in your car will get you slightly better MPG because there is no ethanol in the premium vs 10% ethanol in regular.

If I am remembering this correctly awhile back I read an article about E85 (85% ethanol) and it said you would have to burn 1.5 gallons of E85 to get the same energy output of a gallon of gasoline.

My advice is if you are running premium in order to get better MPG I would be figuring out what your cost per mile is for both regular and premium. Ultimately if you are not saving any money then it is not worth it.
 
#53 ·
My salesman only runs Shell (89)
in his vehicles. He didn't realize Shell was top tier, and said he gets about 80 miles more per tank using Shell. I've been trying to find a convenient top tier station to try, but most are out of my way.

Sent from my ADR6400L using AutoGuide App
 
#56 ·
Octane rating has zero direct affect on fuel mileage. There is roughly the same amount of energy in 87 octane and 93 octane. The changes come from the fuels ability to resist detonation and the abilities it gives your engine. What the higher octane does is let your car run more advanced timing which in turn gives you more power and efficiency. What you perceive as better economy is a just a better running engine which gives you the driver the ability to make up that fuel mileage. It is more noticeable on high compression and forced induction engines. The Corvette that was referenced here will run on 87 but the computer is going to back out a ton of timing to avoid detonation once it starts to detect knock from the lower octane gas. So yes you can run it on 87 but it kind of defeats the point of having a Corvette when it is down 40+HP. Same thing with our cars. with the higher octane the computer can give you more boost sooner and push the timing ahead which will give you more power. If you don't change your driving habits that increased power will mean the engine will not have to work as hard or accelerate as long to do the same amount of work, and hence up goes the MPG.
 
#59 · (Edited)
I agree. On a low compression plain jane motor you are pumping away the dollars for no real reason. If the car isn't detecting knock you can run 114 octane and it won't give you an ounce more power unless you change the tune.
 
#58 ·
Kind of a random thought, but I find Sunoco and Shell to be by far the best gas from a fuel mileage standpoint. Despite not being "top tier" Sunoco consistently outperforms Exxon and Mobil in my experience. And shell is just shell, its giving me some 40 MPG on the highway in just an LTZ
 
#60 ·
Quite interesting to know what sort of RON US has. Here in Malaysia our lowest RON is 95 and the premium being RON 98. Price wise is RM 1.8 / L for RON 95 and RM 2.80 / L for RON 98. To convert it is approximately RM 3 to USD 1. So a full tank here is approximately RM 100 which is about USD 30. What are you guys paying over there?
 
#63 ·
Yeah it kinda sucks, 93 is pretty much the best you can get just about anywhere. I'm sure 98 would work just fine in a Cruze.
 
#65 · (Edited)
..."Top Tier" refers to the addition of specific amounts of "detergents & additives" to normal gasoline, it does not refer to ANY changes whatsoever in either the gasoline itself or its octane number.

http://www.toptiergas.com/deposit_control.html
 
#68 ·
Maybe I missed something, but what's wawa? WHen I tried 93 octane, it was a thursday night, friday was the accident, and that was it. I'm willing to try shell, I had put 93 octane at HEB and noticed a difference right away in the smoothness of the engine.
 
#69 ·
It's a gas station chain. Like Terrible Herbst in Las Vegas. Sheetz is good for a quick bite to eat, not for gas. Same with Wawa.

I've averaged 45 mpg in my commute using 93, and 40-42 using 87. Couple that with the power difference on 93, and the car gets premium from now on.
 
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