: What fuel in a '73?



CoupedeVille'73
08-09-07, 06:33 AM
Hi everyone

I'd like to know what kind of gas to use in the '73 472 engine?
In the ads (for '72) they say unleaded regular is sufficient... (I don't have an owner's manual)
Compression ratio should be 8.5 : 1 or so. No cat.
Sounds ok so far, but since I filled up the last time, the engine seems a bit rougher to me, especially right at start-up.
Any ideas?:confused:

I~LUV~Caddys8792
08-09-07, 12:43 PM
Unleaded should work just fine, as I believe the EPA mandated the change from leaded to unleaded in '72. I'd run premium just to be on the safe side.

CoupedeVille'73
08-09-07, 01:17 PM
Thanks for your answer. They definitely should run on unleaded gas, because since '72 you could buy them with catalytic converter, which requires unleaded fuel. Furthermore the lowered the compression ratio from 10something :1 to 8something :1 by installing a new kind of pistons.
There was a loss of power but its still more than enough :bouncy:
The infos I have, say that it should have ROZ 91, which here in Germany is regular fuel. Premium over here is 95 to 98, even 100 are offered.
So I think regular should do, but I will try premium next time as I think it gives a better milage.
We'll see.

jayoldschool
08-09-07, 05:07 PM
GM went unleaded across the board for 71.