Well this might be a little skewed as its not a blazer, for those of you that don't know I retired the blazer to the winter and towing, with 220,000km on it driving it less each year means I get more years out of it .......So for the summer, i.e. when we don't have snow on the ground I picked up a 2003 Pontiac Vibe GT with a 6 speed, its fun to drive redline at 100kmh in second gear. Was interested in a sonic turbo but in canada they are only offering the turbo in the ltz model and not an option for the lt, and winnipeg is only getting one ltz with a turbo before the end of the year and there will be snow on the ground by then, and then of course i saw the 2013 sonic rs which looks nicer So basically havent decided how long im going to keep the vibe gt if i do get a sonic or just decide to stick with the vibe for a while. Picked it up with 82,000km on it for 7300......ones at the dealerships here go for 9500 with 140,000km on it.

So anyways to the point
The GT version has a high compression engine which of course needs premium, now I have filled it up with regular and it runs fine (no knocking etc.) but it definitelly has more pick up with the premium. So this led me to the premium vs. regular fuel economy debate.

I have not had enough data to come to a conclusion, I ran 2 tanks of regular for city driving but have only gotten 1 tank of regular on the highway. I got 1 tank of premium on the highway and noticed a 20% improvement in fuel economy(thats huge!), got 6.6L/100km on the highway at 110kmh, the governments fuel rating for the highway on the vibe is 7.1. but i still need to get a few more tanks of each to make this more conclusive. I have a tank of premium in for the city now and will see how it compares. But with something that drinks less gas than the blazer it takes a bit longer to get the data.

This is in a high compression engine, now this leads me to ask if anyone has tested this out in the blazer and what they have come up with. I have a friend that did this in 4cyl toyota venza that is not high compression and takes regular and claims a 10% improvement in fuel economy (Which roughly evens out with the extra price of premium).

 

Aw.. geez. And we were just wrapping up the 'oil filter ' issue.

like you say it all depends on the design compression ratio. The mfr will recommend what runs best and most econamically.
I'll draw on my owning and driving the crap out of a 84 SVO 2.3L turbo. It had a switch to limit boost to 8lbs opposed to 18 and labelled it Premium Gas. normal performance was better on regular grade until you kicked in turbo. Verified when wastegate actuator diaphragm broke and I disconnected the actuator to defeat any boost.
I then ran regular on next fillup and performance and mileage improved a lot. Because the turbo engine had lower compression ratio than std 2.3.
This engine had a knock sensor so the ECm could optimize timing... otherwise the exhaust valves would take a beating under cruise.

And that's something you wont know until it's too late.
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Obligatory pettyfog anecdote:
Way many years ago Gulf came out with a Super High test {IIRC about 97 octane} they called Gulf Crest
They advertised it as 'fixing what ails your poor performing engine'.
It sold great for a few months till the word got around and the repair shops had more business than they could handle. Then the obvious truth came out.
It not only removed cylinder and valve deposits but valve seats and faces as well.

I was only a kid at the time but the Crest pumps suddenly disappeared faster than they had gone up. Reckon the lawsuits were starting to hit home. It was a stupid idea and I'm pretty sure Gulf Marketing overrode their own engineers when they did it.
Read this full page 'info-ad' in Life Mag circa 1961 and laff.
Red Barber was the most highly respected national sportcaster of the time.

"After hours of racing {at Sebring} the engine looked like someone had been in there polishing."

I bet. The small print recommended a tank every 'thousand miles or so'. Which would mean every third tank. But everyone knows if some is good, more is better.. bwahahahahaha.
I'm pretty freakin sure those Sebring racers had their heads milled and only rule on fuel was available pump gas.
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Here's something to ponder. If you baby your engine and run typical gas, putting in high test might actually improve performance at least for a while due to combustion chamber deposits which have the net effect of raising the compression ratio.

 

I run this test with every vehicle I own just to see what happens. I typically run 2-3 tanks from my select stations for each fuel grade. Some vehicles are more particular than others though.

My '01 Bonneville SSEi required premium, especially after tuning it and dropping on a smaller pulley. My '00 Bravada returned the best mileage on 89, but the cost still wasn't in favor of using it so I stuck with 87 even after the hypertech tune. My Rainier after the PCMforLess tune got the best mileage on 93 octane (along with the widest smile on my face during WOT runs), but 89 was the lowest $/mile and didn't show much of a difference in times while data-logging. I run 89 in the Tahoe because that gets the best $/mile results.

Here's a quick search for a few of my replies on the subject of octane & mileage.

 

Yes, the vibe runs an 11:1. curious to see the difference for city driving, I need to get more miles in on the highway and get some mid grade trips in as well so I can get everything pin pointed. I have never fully run this test with the blazer, have dumped the odd premium in once in a while when a station ran out so they decided to give premium for the price of regular but have never made an effort to compare. So was wondering if anyone else has with the blazer, with the 9:1 im assuming there would be no beneficial or cost saving to dump in premium. For the vibe if things hold true it will be for sure

As for me Im thinking the blazer needs a seafoam treatment, 220,000km and over the past 6 years my total average economy is 17.75 L/100KM

In the city i have been averaging 19-22 L/100KM which is actually up 2L/100KM vs. when i first bought it 6 years ago. Which I am chocking up to the new more aggressive tires, 1.5" shackles, no plastic valence on the front and a roof rack. Now my last trip back from bc i was hauling a trailer on the highway and was getting 17-19 L/100KM one section was on premium but my excel file seems to be all messed up for some reason i cant figure out, looked at it one second it was good looked at it again and it was messed up...but i didnt seem to notice any difference. without the trailer on the highway generally between 13 and 15 L/100km.

Will see what happens when i get more data with the vibe, if anyone has found anything out with the blazer, differences let me know.

 

My Jimmy doesn't get better mileage on premium.

My old 92 grand am GT got WAY better mileage on 89 as apposed to 87 and the same mileage on 89 and 91/92/94

 

This is like an equation lol. Measure the price of regular and how many mpg's you get to the price of premium and the mpg's you get. It's really not worth running premium in the blaze because it is not tuned to benefit premium, nor does it have forced induction. So I usually run regular unless a station has a good deal, in my mind, on premium or gas in general. So my rule of thumb for vehicles in general is regular unless it's a forced induction, V10, V12, or it is tuned and setup for premium.

But on a side note, they used to sell racing gasoline in Concord, NC. I always thought about getting a few gallons but that crap was around $5.00 a gallon for 105 octane and I couldn't pull myself to do it. Just saying.