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Discussion Starter · #1 ·
I usually use 94 octane, but desperate and unable to find a Petro-Canada station, I settled for 91 octane at Shell.
Have been noticing a distinct lack of turbo boost ever since.
However the fillup coincided with the start of a heat wave here.
What do you guys think -- could going "down" to 91 octane (which is premium at most stations) cause a noticeable drop in power? Could hot weather be he cause?
All theories welcome!
 

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What I would give to find 94 octane around here. I live in South Dakota and to be honest I am lucky to find 91 octane most of the time. In fact if you go out west most pumps are 85/87/89 (yes, they can sell 85 in the mountains).

A 3 pt drop if all you use is the "really good" stuff could have a noticeable change. On the opposite side of that the 89 octane around here is incredibly cheap (mixed with 10% ethanol) and I've been using it a lot lately for the 50¢/gal savings. But the motor has seemed really rough. I upped it to 91 octane on my last tank and it's good as new! I think I will just bite the bullet and stick with the good stuff unless it gets really cold out this winter.
 

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Both are good theories - I thought my car lost a certain zip when I lived in California and could only get 91. And hot air is less dense, so even with the turbo, less oxygen is delivered to the turbo. Things seem much better with air around 50 of 60 F.
 

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My guess is heat. I've owned several turbocharged cars, and every single one felt more sluggish as it got hotter outside. 94 octane is a waste of money imo. I am not a tuner by any means, but my understanding is the car will run it's best at the octane Saab calibrated and tested the engines with. I had a good friend who was an engine calibrator for the srt team at Dodge. He did the neon srt-4, and was talking about how the 94 is a waste of money, and said the 100 octane unleaded will actually hurt performance on a stock or stage 1 motor. (stage 2 had a race gas calibration an option and made a huge difference) On that engine, 91 was fine, 92-93 might be marginally better, and anything else was just overkill. My wife uses 89 in her car, and I will do the same when I get mine.
 

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Things seem much better with air around 50 of 60 F.
I will agree. This car seems to do better in the fall weather. Too cold and it's all creaky. Too hot and it feels like you are working it hard like a horse. Fall temps? Everything on the car seems to be perfect.
 

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I will agree. This car seems to do better in the fall weather. Too cold and it's all creaky. Too hot and it feels like you are working it hard like a horse. Fall temps? Everything on the car seems to be perfect.
;ol; it's funny that I prefer Fall only because of how my car drives. Although most of our Winter is 50-60 here :cheesy:
 

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Discussion Starter · #7 ·
Now that I think of it, the heat wave started before I filled up with 91. So I am leaning towards the gas theory. Perhaps heat plays a role too though.
I would say the "turbo boost feel" is reduced by almost half.
Will fill up with 94 in a few weeks and post my findings.
 

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Discussion Starter · #8 ·
The heat wave broke, we are now enjoying temperatures in the high Celcius teens (60s in Farneheit). And I am happy to report that I enjoyed full turbo boost once again.
So it would appear that the outside temperature has a major impact on power. And switching from 94 to 91 octane, not so much.
 

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You might think about hosing off the inter cooler, which sits behind the lower grill. It can't hurt if it's dusty or buggy. Like I said, my car is less peppy in hot weather, but I don't notice the change being as dramatic as you describe. Then again, we don't usually drop from the 90s to the 60s that often.
 

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IM gonna have to say heat. On really humid days my car wont boost pass 5lbs in 1st through 3rd gear.
 

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If you traveled out of town when it lost power that could be due to if there was a significant altitude difference.

I went from Irvine ky where I live at 680 feet to kingsport tn at 1208 feet and I noticed a big power loss....
 

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91 or 94?

Where I live theres only shell 91 but in Ottawa I get 94 petro can and I notice a very little differance right when I add the new gas ,but I do mean little, the heat weve been having makes a bigger differance.Particularly in the city.I change back and forth all the time ,but only those two types of gas!
 

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Discussion Starter · #14 ·
On second thought, I'm going with the Fuel having the biggest impact on power. We have been sweating through a heat wave this past week but my car's turbo was FULL ON STRONG even with 4 people in the car this past weekend, after I filled up with 94-octane at Petro-Can.

The heat wave did bring a new issue to my attention: I need a freon recharge! ;oops: :lol:
 
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