I run only synthetic oil in my sixes that have been rebuilt. I just switched to Mobil1 15W-50 extended service oil -- it has 1200 ppm zddp. See this chart: http://www.mobiloil.com/USA-English/MotorOil/Files/Mobil_1_Product_Guide.pdf It's $8 per quart -- but with a 15,000 mile change interval, it's cheaper than mineral oil. You also produce less waste and crap to recycle. I don't know about yours, but my motors are getting more and more expensive to rebuild! (ANd I get fussier about them as I get older :-) Not sure if I'll change a filter/add quart half way through. At that long interval it might be worth oil testing at 10K. Certainly a waste of money/effort on leakly oil burners. Times change! On Mon, 17 Mar 2008, Sandwich Maker wrote: > " From: ksiroonian@xxxxxxx > " > " > " Also , on the oils and the zinc- I went to wall mart- saw the pre 1988 10w 40 oil for 1.39 a quart, and also the chevron, shell and mobil 10w 40 diesel oils, about 9.19 a gallon, all very reasonably priced. I have been using the valvoline high mileage stuff in my cars, none are for racing or other than light driving, going to a car show, under 500 miles a year. > " ?so for the reader's digest condensed version... is it still better to use these above oils with the extra zinc in them, or is it not needed, and are you guys recommending that stuff only for engine rebuilds and racing and such? Or is the GM EOS ok or even needed? I know in the AMC repair manual it does say to coat new engine parts in a rebuild with the AMC EOS, and I know for years dealers would add it to each oil change, though I always thought it was just a profit builder, like the 3 most profitable words in America.... lather. rinse.. repeat. I know many of you are into the racing and the performance and things so just wanted to get the readers digest condensed version. > " Regards, Ken. > > i agree with the experts; your engine was designed to use high-zinc > oil. btw the sae set a spec on it [the first? anyone know?] in the > late '70s by testing production engines with various zinc levels and > measuring wear. mega-zinc oils like the joe gibbs break-in stuff, > well that's self explanatory - you don't and shouldn't run them all > the time. adding eos on top of high zinc oil would accomplish much > the same thing, not routinely necessary. adding it to today's low > zinc oil isn't the same. > > i'd use the walmart stuff. i'm tempted to run it in my '94 4.0. > > do the diesel oils have an 's' rating at all, or just 'c'? and btw be > aware not all diesel oils have high zinc any more either. api 'ci' > and 'si' were the last high-zinc specs, but some diesel oils are now > rated 'cj'. iirc still more zinc than 'sm' car oils though. > ________________________________________________________________________ > Andrew Hay the genius nature > internet rambler is to see what all have seen > adh@xxxxxxxxxxxxxxxxx and think what none thought > _______________________________________________ > Amc-list mailing list > Amc-list@xxxxxxxxxxxx > http://splatter.wps.com/cgi-bin/mailman/listinfo/amc-list > _______________________________________________ Amc-list mailing list Amc-list@xxxxxxxxxxxx http://splatter.wps.com/cgi-bin/mailman/listinfo/amc-list