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Trucker
09-20-2002 23:27:06
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Re: Diesel oil in a car engine? in reply to John, 09-20-2002 04:33:45
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I was a mechanic for a long time,I rebuilt diesel engines.I dont know about real new engines,its probobly better to use what they call for in them,but on old engines,you can use 15-40 diesel oil in any engine.The difference in diesel oil and gas oil is that diesel oil has more detergent in it.Now if you have an old,old engine that used straight weight oil,and for years and years was not rebuilt,the extra detergent could knock the crud loose in the engine and plug up something like an oil gallery.I know from experience that an engine that used series 3,or 30 weight diesel oil,would be a lot dirtier inside than one that used Shell 15-40.Now there are other brands,but I dont know about them.Shell was first,and I use it in my truck.I know kendall is good Diesel oil in 15-40,the others I dont know,but they have to pass tests and it should say on the label what tests they passed.Ive had the best luck rebuilding an old motor like for a pickup,and useing Shell 15-40 in it.Real old motors like caterpillars,that called for 30 weight,series 3,or whatever you call it,would leak out of the mains if you switched to multigrade oil.They designed new seals that fixed the problem,and if you get a piece of equipment that has been used since the late 80s,and has been rebuilt,chances are that it has the new seals in it.Now when people used series 3,we changed rod and main bearings in cummins motors about every 100 thousand miles.Now that everybody uses 15-40 Shell or something thats passed the same tests,its not unusual for a diesel engine to run 7 or 800,000 miles and not be touched by a wrench.I like to look at the bearings after about 300,000 miles,but I change them when I look at them,and usually I think I wasted my time,they would have gone a lot further.I would say that unless somebody has another reason besides breaking loose sludge,or a new engines tolerances,diesel multigrade would be good,and most likely better than gas oil in any engine.I also noticed that if you have an engine that leaks a little bit with 10-30,might quit leaking with 15-40.Also if a motor is so dirty inside that the diesel oil breaks the crud loose,it probobly needed to be rebuilt anyway.It might run for years if you didnt put the diesel oil in it,but it might not run but a few minutes and the stuff fall out of somewhere and clog a gallery.I know the oil is better,and diesels run day and night up mountains and in all conditions,and with longer service periods.You just have to use your own judgement on a motor,and if its allways had the oil changed,didnt idle much,and clean inside,I think it will work.Also it needs to be from the time multigrade oil was specified for the motor,as I know old cat seals will leak,other brands werent so bad about that,but they might leak some as 15-40 is lighter than 30 weight a little when its cold outside.Most likely even on an old motor if you put new seals in,they are made for multigrade oil,but you need to ask,and cosidering how much better multigrade oil is,insist on seals that work with this oil,as the old oil is outdated and may not even find it.
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