So for those that use premium, what kind of mileage increase are you getting?
10%? 20%? With what octane rating?

 

About an 8% increase. Boy I wish it was 20%! In warm weather, that is 50+ fahrenheit, I averaged 25mpg with regular (87 octane). With premium (91 octane), I average 27mpg. I put on 15-17k per year of mixed freeway & street driving. That works out to a little over $100 a year (or $2 whole dollars a week!) in cost savings at $3 a gallon. Keep in mind too that I'm a fairly aggressive driver. I punch it when I feel I need to or just plain want to. I do not subscribe to any form of hypermilling. That would just drive me crazy.

Its a waste of time to try this test in colder weather, i.e. winter. Between the "winter" blend of gas, longer idle times (such as using the remote start), and warm up periods, you really can't establish a good baseline.

 

Ah...so you only get the milage benefit sometimes...your taking the best results and averaging it over a year...how about actual numbers for the whole year?

 

Huh? Maybe I wasn't entirely clear. I ran this test for a month with regular, and a month with premium. I get a consistent 27 with premium in warm weather, not just sometimes. Why would I want to waste an entire year running regular just to compare?

I don't factor in winter/cold weather simply because no car will run at its optimum in low temps, especially given the fact that we have to use an E10 "winter blend" . EPA testing is not done under those temps and conditions either. I get about 25 in winter. Its getting warmer here now, mid 50s, and in the last two weeks I went from 25 to 27 avg per fill up. It's not rocket science to understand that if I used regular in the winter, I would not get 25 but probably only 22 or 23. So the benefit of premium is still the same.

 

E10 is year round... what I'm saying is you tried to do a year round comparison on savings and its flawed! You have no idea what you will get under anyother condition with either gas. You might find because of weather the split is larger under one extreme compared to the other....for alll we know your comparison was done under ideal conditions with 93 and not so great with regular.(Popular means of comparison between competitors), intentional or not.What makes me question is the ratio of those who say yes against those who say not enough to make it worthwhile.Who knows maybe YOU got lucky and YOUR car is different in some way to take advantage of this, others may not be.Maybe your timing is on one end of the spectrum where reg does not work so well, or the compression is slightly higher where as the knock sensor is working overtime on reg gas..or maybe your not so lucky.............
Also check your math..it cost 9 cent a mile on 91 and 8.9 cent on reg at a 2 mpg split......

 

Of course its flawed. I'm not a scientist. If you have the time and energy for all that, go for it. I don't, and neither do a feel a need to split hairs and get the numbers down the penny and 10th of a mile. I'm pretty confident from the testing I have done, as well as my experience of monitoring mileage for many cars and trucks over the last 30 years, that the cost is enough of a gain to make using premium worth while for my purposes. I also NEVER said I was for or against using premium. I only stated that if you haven't done any comparison, you'll never know if its worthwhile or not. As far as weather, I have seen a 10-15% loss of mileage in cold weather on every car I have ever owned regardless of fuel grade. Why would I need to go through all that testing again in the winter with my HHR to more than likely re-learn what I already know? Even if regular got better mileage in the winter, it still wouldn't amount to more than a dollar or two a week. And for that I'd rather have the performance anyway. As I've said all along, its a wash, but your mileage may vary.

BTW, this is not the first premium optional car I have owned. My old Catera did not get better mileage or performance on premium. It did run smother though. So I compromised and ran mid-grade in it.

I guess I'm not really getting why you are pressing so hard on this.

 

That is very true...that's the same with my truck.

 

I've noticed my car runs worse on regular, I always use premium

 

With the option of 3 grades, I typically try a full tank of each and calculate the milage and make note of the performance differences. I have found on 2 previous GM vehicles I owned that the mid grade was worth the extra money.

 

Just to add fuel to the fire, what about e85 and power increase? I already know mileage suffers dramatically on 85 then any other grade.