GM Engine ID... [Archive] - The Supercar Registry

WILMASBOYL78

01-16-2016, 04:50 PM

What does the "L" in L78 stand for??? I notice all GM engines seem to have an "L"....and is there any method to the numerals like "78" or is it just by chance??

wilma <<GRAEMLIN_URL>>/hmmm.gif

BLACKLS5

01-17-2016, 02:14 PM

Tom, GM seems to use an alpha prefix for their RPO options then and still to this day. "A" are usually power options, seat, window, seats, etc. "B" are molding options, "C" heating and cooling, "D" stripe and decal packages. Of course "M" are transmission options and "L" engine options. I could go on and on but I think you get the idea.

I've worked in the parts department at a GM dealer for 29 years. GM used to send out little booklets every couple of years that listed what all the RPO codes were. That was before computers became common. Now we just type in the Vin # and it brings up all the options the vehicle was built with. I hope this helped....Troy

Kurt S

01-22-2016, 08:46 PM

I once heard the L originated for Locomotion. There was some historical info to back that up, but it was many years ago. I don't recall the origins of the M, but it was in that same article.