87 OCTANE VS 93 OCTANE

[WONKABOY]

WHEN I FIRST GOT THE CAR I WAS USING SUNOCO 93 BUT FOR LAST LAST 3 WEEKS SINCE THE GAS CRISES I WAS USING 87 WELL THE CAR SEEMED TO RUN LOUSY WITH IT, BECAUSE TODAY I PUT ABOUT 10 GALLONS OF 93 IN TO MY 1/4 TANK AND AFTER AWHILE THE IDLE AND PERFOMANCE WENT BACK TO NORMAL , HAS ANYBODY EXPERIENCED THIS WITH THEIR 81 STOCK WHILE USING DIFFERENT OCTANES?

Rick

 

[GT1981]

I'm using 89 octane in my stock 350 engine and have had no problems with idle or performance since I bought my '81 in Nov 04. I admit I have not tried using octane above or below 89.
Greg

 

[bill81vette]

I've only put 93 octane in mine.and then only name brand gas!

 

[81kix]

I only use 93 or 94 octane

 

[oceangal]

I have only run 93 (Sunoco) since I bought the car (almost a year ago) and the prior owner was using it so I figured I should too. I am afraid to try the lower grade and for the difference in price vs the amount I actually drive it, I figure why not.
Sounds like you did good by switching back.


Lori

 

[Vettehead Mikey]

If there was actually some change in idle quality between the two gasolines, it was not due to octane number. Maybe you just got a bad tank.

The only difference that can actually be perceived while driving is whether the engine knock/pings. High octane gas has no ingredients that would allow an engine to start more easily or idle/run smoother

 

[smithjw]

I'm kind of surprised that many of you are using high octane gas in your '81. Like Mikey said, higher octane gas does not make your car run better except for one instance, and that would be that you have made mods to your standard engine and one of the things you have done is advance your timing. In this case, you would need a higher octane or you would start getting a ping. Octane is always discussed in just about any automotive forum that I have ever read. Standard rule of thumb is to always check your owner manual and it should state the octane that your engine requires. For the '81 it's regular or 87 octane gas, unless you advanced your timing. So, with the price of gas these days, you'd be spending too much if you were always buying higher than 87 octane gas.

 

[Dave L.]

I use 87 octane. My car has 115,000 miles and never pings,runs perfect. IMHO its a complete waste of money to use any octane higher than 87 in a motor that only has 8.2-1 compression ratio.

 

[81kix]

I use 87 octane. My car has 115,000 miles and never pings,runs perfect. IMHO its a complete waste of money to use any octane higher than 87 in a motor that only has 8.2-1 compression ratio.

Different strokes for different folks

 

[zachh]

I nave a 79 l82. Ive run it to almost E twice. Its ashame I ve only put 200 miles on it, and the E is a familiar thing. I put 93 in mine, Im 16, so I thought the only difference was about 30 cents. It was cheaper, so I put 20 gallons of 87 in it. It ran fine for about 2 minutes, then it started to idle rough and ping/ knock, and miss. She wont run on anything but 93 or more. It has very few new parts that make a difference, new cam, 50,000 volt (direct replacement) distributer, and a few other parts like that.
zachh
mine: 79 L82

Its not the fall that kills ya, Its the sudden stop!

 

[Dave L.]

Standard rule of thumb is to always check your owner manual and it should state the octane that your engine requires. For the '81 it's regular or 87 octane gas, unless you advanced your timing. So, with the price of gas these days, you'd be spending too much if you were always buying higher than 87 octane gas.[/quote]

Amen

 

[xlr8shn]

Running 89 Octane with Ethanol, - gasp -

Stock L81's are low compression (right?). No need for higher octane to prevent ping, since good quality 87 or 89 octane will suffice... UNLESS your engine has been modded (higher compression heads, cam, pistons maybe). Though you can pay and run whatever octane you can afford.

Now, high compression plus forced induction demands no less than 91+ octane. Even strapped on Methanol injection to cool the intake charge down further and increase octane.

 

[74bigblock]

If there was actually some change in idle quality between the two gasolines, it was not due to octane number. Maybe you just got a bad tank.

The only difference that can actually be perceived while driving is whether the engine knock/pings. High octane gas has no ingredients that would allow an engine to start more easily or idle/run smoother

Not true... the higher the octane, the slower the fuel burns... the slower the fuel burns... the more idle you need to maintain the same RPM.

 

[G Winter]

I have been running shell 91 V Power in my 90. (91 average) At times I don't get around a shell station with the V Power and put COOP premium in. Seens that the milage drops 1 to 2 mpg. This is checking on 2 or 3 consecutive fills.
I also tried the Shell reg 87 (average) and had the same results as on the COOP premium. BTW COOP is a farm related bussiness for you city people.
I have never noticed any pinging but all around the engine seems to run smoother on the V Power. The manual does state, premium fuel recomended.
The C4s tend to run very warm under the hood which I believe could have an effect on the grade of fuel required. In cool weather the fuell grade may not have as much affect on the way they run. In hot weather I would never run the regular,if I did I would have a very light foot.I also will not run ethenol in the earlier TPI engines including the V6. Even my wife noticed when I tried ethenol in the 89 Riviera thats how badly it ran. The newer OBD II cars may not have the same issues. A side note, I had my plugs out to check them just before cruisefest and with 8000 miles on them they had a very nice light tan color with no hot specs on them. I do believe good fuel helps keep everything cleaner. Cut rate gas just plane sucks. You usually get what you pay for.

Glenn


Glenn

 

[xlr8shn]

I also tried the Shell reg 87 (average) and had the same results as on the COOP premium. BTW COOP is a farm related bussiness for you city people.

I always use BP 93 in my C5.

When Dan @ FLP (Naperville, IL) dyno tuned my car he was telling me to AVOID Shell gasoline because of MANY customers' cars that would show knock retard even with "high octane" Shell gas. Same customers would reschedule dyno time and return with BP or other non-Shell 91+ octane gas and have MUCH LESS knock.

Coming from a reliable tuner with dyno & computer logging software, I will never use Shell gasoline. Sorry.

 

[Allthumbs]

Octane for an '81

I am new here.. but my owners manual says to use gasoline with an octane of "atleast 87" and an 85 may be used in high altitude states. P. 2-3. I have been using only 87 octane and have had no issues at all .

My thing is to avoid filling when the gas truck has just left the station !

Tom