Re: Suggestions for a gas additive / lubricant?
Chevron's opinion is here:
http://www.chevron.com/products/prodserv/fuels/bulletin/unld-gas/
It slightly contradicts Mercury Marine's current posted recommendation. If you believe the fine print Mercruiser writes on their fuel recommendation website, it would seem that they didn't start using hardened valve seats consistently until the 1987/1990 range on their non-EFI and non-supercharged models. I , too, find that hard to believe, but I don't know why Mercuiser recommends a valve lubricant right there on their website for seemingly most every engine older than 1987/1990ish. All very interesting...
http://www.mercurymarine.com/fueloil_recommendation_faqs
The introduction of unleaded fuel is one thing but I don't think gives us the answer (E-85 was just introduced recently, how many of our boat motors run on that?) It seems from my research that leaded gasoline wasn't fully taken OFF the market in the US until approx 1986...so this may be the basis for Mercruiser's recommendation. I have a personal memory of pumping leaded fuel into my 1968 Firebird after I was married in 1982....so I know leaded fuel was still readily available at that time. And given the marine engine industry's tendency to postpone doing anything non-required until the last possible minute (just look how long is it taking them to change to very basic environmentally friendly things like EFI and sealed fuel systems? They're STILL selling carb'd models and many fuel tanks vented to the open atmosphere TODAY! Very sad, in my opinion) maybe it wouldn't surprise me if they were still dumping some old-stock non-hardened valve seat heads to the public well into the 80's, and they would have required leaded fuel for valve cushioning...
DISCLAIMER...I'm speculating and I freely admit that I do not personally know the answer(s) to above.
Does anyone here happen to have an early 80's Mercruiser owners manual or shop manual that was PUBLISHED back then and is not a newer reprint? I'm sure they made fuel recommendations at the time also...would be interesting to see if it was different than they recommend now.
