It says in the owners manual that if you use regular unleaded instead of premium, performance will suffer a little. Has anyone done it, and if so, how much does performance fall off? Around here premium is headed towards $1.85/gallon. That's cheap for beer, but pricey for gas.

Thanks
'90 IROC 5.7

 

Mine is a 305, but I've never used anything but regular unleaded in it. Try it, see if it pings or not. If it doesnt, you are good to go.

 

I'm paying near 2 bucks a gallon for regular...been using regular for just about ever....

 

i used regular in my L98 iroc, no problems.

 

I use reg. unl., always have, always will.

 

I used it and it ran like crap

 

I use 87 octane all the time save for running some 93 thru every couple of months. I honestly couldn't tell much of a difference. If all you've ran is 93 for years and then you switch to 87 you'll prb have some pings, but otherwise it shouldn't be a prb. BTW our gas is going for $1.37 for reg. and $1.47 for prem. so it sounds like I have it made when it comes to gas prices.

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1986 Berlinetta, 2.8L, newly rebuilt 700R4, 3.42 Posi. 127,000 miles and counting.
I've come to realize that I'm gonna have this car till it pukes for good, b/c I'll never be able to bring myself to sell it.

 

Why would it ping going from 93 to 87? Engines dont get used to fuel like people get used to food.

 

Not to disagree poablo but I see it like this, as I have always been told, the metal actual does get used to a certain style of driveing and certain oils and gas.
I personally use reg. unleaded, but I have heard some stories of people switching lower octane gas and they say it runs worst.
I personally couldn't really tell but everyone gets used to there car and can tell more about their own car than I can theirs.

 

One problem I've noticed whenever I used regular, is that my gas mileage goes down. I get about 10% better mileage with the premium. This makes the price just about the same. I have TPI engine though, you may not see any difference with the lower motors.

 

regular gas 87 makes it ping i have to run 93 and i get better mileage with premium @1.75 a gal, the price sucks but to keep her from pingin its worth it.
91 RS 305 TBI
freshly repainted mystic teal that looks awesome

 

my car gets better gas milage on the 93, so much better that it doesnt make it worth getting the cheaper gas, it wnds up costing the same

regular- 15-16 mpg highway/city

premium- 22-15highway/city


Steve

 

I've always used 93 octane in my IROC and I get nearly 30 mpg on the highway, but about half of that in the city. 87 octane kills acceleration in my vehicle. No pinging but the car feels like it's running on diesel.

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'88 IROC 305 TPI
Gutted airboxes
160 degree T-stat
Advanced base TPS voltage
Relocated IAT sensor
Momo steering wheel
Ram-air setup coming soon
Flowmaster muffler

 

don't the computers in our cars actually learn over time and change the spark curves slightly? not positive but i thought i read something about that. also know that my gas mileage jumped like 4 mpg on the highway after i disconnected the battery for about 15 min one day. got almost 50-60 more miles per tank, 2 different trips to FL from NY

 

I have to agree with JJ. When I've used premium gas, I get better mileage than with regular unl. Either way though, I'm probably paying the same cause premium costs so much more and a full tank of it doesn't last that much longer than just regular. As far as performance, other than mileage, I've noticed nothing different.

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ICQ #: 77308896
AIM: Ezekiel2sc
2.8L MPFI w/ K&N filters & homemade ram air
5 speed manual
3.42 rear axle
180W Clarion CD Deck
Pioneer 4*6 in front
Polk 3 way 6*9 in back

[This message has been edited by SillyWabbit (edited September 18, 2000).]

 

as far as i know the ECM doesnt give 2 rats about what the octane is of the gas you are using.. all it looks for is ping, and if it pings it cranks down the advance.. if you are pinging on 87 run 89, etc etc.. gas is gas, it's no cleaner, and it deosn't have more "power".. all it is, is less susceptible to pinging, period... i notice no difference at ALL in my '86 or '87 IROCs.. if you are pinging on regular gas and you have a stock engine, you need to be turning your distrib back a bit because your base advance is too much, it should be near 6 degrees.. just my $0.02

 

Here's a theory: Your car might not run as well if you ran premo for a while, then switched back b/c your computer "learned" that it was using a higher octane fuel--meaning it saw it was using the certain timing patterns all the time and thus switched its everyday parameters to control timing and such for that octane fuel. When the fuel quality is degraded with lower octane gas, the computer is still thinking that it is running premo, so you have some minor problems. Eventually, the car would re-learn to run "optimally" on regular gas again if that's what you stayed with.

XXX.

 

I started using reg. gas when the price for 93 octane hit $1.75 a gal. a few months back. Reg. gas is at $1.57 a gallon (cheapist) when I gassed up today. I don't see any differences since switching to reg.

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• 1991 Z28
• Ultra Metallic Blue
• 305 TPI
• 5 Spd Manual
• 3:08 rear axle

members.fbody.com/rwendt/

 

i always use 92 and personally it feels like im running on water if i use anything less.

here in san francisco i pay $2.20 a gal for 92 premium. you are all lucky gas is so cheap. 87 regular is $2.00 a gallon.

to me its worth it to pay an extra $2.50-$3.00 to atleast think i am getting better gas mileage and performance

 

Everyone here should start using priceline.com for gas. I save at least 15 cents per gallon.