what fuel should I run in my 1968 GTO with 400 big block 4bbl?

Asked by May 20, 2015 at 01:04 AM about the Pontiac GTO

Question type: General

It has been so long since I put gas in a car this old I don't remember if we were still using
leaded fuel. I was working in gas station in 1970 and remember selling gas for 23 cents
per gallon with different octane ratings but I think all the grades contained lead.

4 Answers


That's correct. Any GM made before 1971 used leaded gasoline. Your GTO requires premium. I used to fill up my '70 Catalina, with the same engine, with premium, lead substitute, and octane booster at each fill up. Without the octane booster it would diesel when I shut it off. HTH. - Jim

1 of 1 people found this helpful.

Back then the octane ratings were a lot higher than they are now, I believe that engine used premium fuel and that was 101 octane, so now you can't get that fuel, so you have to buy the highest octane you can get, put in a bottle of StaBil Marine additive, this helps with the ethanol in the fuel, then add some lead substitute, that's for the old valves and seats, then try it, if the engine pings then you have to add a bottle of Octane 104 and hope that does the trick. There was a time when you could get 101 octane from an airport, but I don't think you can do that any more.

2 of 2 people found this helpful.

I was to working in a gas station and it was .53 c a gal boy would it be great to pay that again

You can use avgas... 105 octane, or race fuel... 110 octane.

Your Answer


Looking for a Used GTO in your area?

CarGurus has 446 nationwide GTO listings starting at $4,995.


Pontiac GTO Experts

  • #1
  • #2
    Norm Davis
  • #3
View All

Related Models For Sale

Used Pontiac G8
9 Great Deals out of 444 listings starting at $5,400
Used Chevrolet Camaro
454 Great Deals out of 31,411 listings starting at $1,450
Used Ford Mustang
600 Great Deals out of 39,164 listings starting at $1,895
Used Chevrolet Corvette
173 Great Deals out of 17,500 listings starting at $3,000
Used Pontiac Firebird
9 Great Deals out of 770 listings starting at $4,000
Used Dodge Challenger
255 Great Deals out of 25,103 listings starting at $7,750
Used Dodge Charger
469 Great Deals out of 33,551 listings starting at $1,999
Used Cadillac CTS-V
11 Great Deals out of 617 listings starting at $6,599
Used Ford Mustang SVT Cobra
7 Great Deals out of 315 listings starting at $4,795
Used Chevrolet Silverado 1500
2,657 Great Deals out of 173,972 listings starting at $955
Used Chrysler 300
347 Great Deals out of 19,430 listings starting at $900
Used Mitsubishi Lancer Evolution
10 Great Deals out of 577 listings starting at $12,999
Used Pontiac Grand Prix
16 Great Deals out of 2,679 listings starting at $1,750
Used Subaru Impreza WRX STI
27 Great Deals out of 629 listings starting at $9,490
Used Chevrolet Impala
592 Great Deals out of 34,467 listings starting at $900

Content submitted by Users is not endorsed by CarGurus, does not express the opinions of CarGurus, and should not be considered reviewed, screened, or approved by CarGurus. Please refer to CarGurus Terms of Use.