I went to Synthetic oil at 145k. My truck now has 155k with no oil leaks or problems from the switch. I found that I had to change the oil at 1000 mile intervals for the first three or four oil changes as it would be jet black by that point. I'm now up to 3k intervals and all seems well.
One thing: I did notice an increase of ~2 mpg in gas mileage (went from ~16 to ~18 mpg in city, and ~18 to ~21 on highway) through the last six tanks.
Typically you would not really want to switch at this point. There is sludge built up inside the pan and whatnot and the higher detergent synthetic oils will break down this sludge and can cause problems.
If you do want to switch then run a can of the oil cleaner through the engine and then do a filter change, then add synthetic. Do a few oil changes quicker than normal. You should be okay. But, the question is why would you change to synthetic after this many miles. The damage has already been done.
I switched my Trooper to Mobil One after I bought it, at 110K. Doesn't burn any oil to speak of, and I would like to keep it that way. I am not worried about switching to synthetic in the least. I have used Mobil One for 20 years with nothing but good results.
:twisted: So there you have it, any time a synthetic oil question is raised, you will get the entire spectrum of possible answers... :twisted:
You could go with semi-synthetic on one oil change, then go to full synthetic the next, might be just paranoia on my part but thats what I like to do. And make sure to get a good oil filter to pick up the stuff that might break loose during the switch.
Don't get me wrong here, I'm a big fan of the man made slippery stuff.
Nothing but Amsoil goes in my 98 Passport, but it's been that way since about 15,000 miles.
My 88 Trooper had 203,000 miles on it when I bought it. Is there any sense in putting syn. in it? Not really I didn't drive it enough to worry about it. Heck I didn't put 3000 miles a year on it. So it got regular oil.
contraversial subject indeed... to syn or not to syn.
A clean engine- is less likally to generate problems... crud can cause things to stick, and plug up the flow of oil, thus generating MORE problems. switching to synthetic, can help clean out an old engine- and provided none of the "removal" of "gunk" happens in any large chunks, there shouldn't be any problems... Like others have suggested, keep the change interval low for a few changes because the synthetic will be removing gunk and filling up the filter and wearing itself out faster.
The detergents found in modern oils, are not highly abrasive and aren't designed with the intention of removing large pieces like paint stripper. They slowly soften the upper layers of the buildup, and it is slowly removed as the oil passes over the loosened grime.
If you are willing to bite the bullet on the cost- switching to synthetic, will help slow down the wear on an engine, even when old- sure, there is damage already done- but slowing that damage down now can still mean more miles.
There are alteratives that may be more cost effective and return decent results...
1. Chevron Delo 400, (diesel oil) is formulated from base stocks that are considered 1 "step" better than a regular dino oil(group II+). Includes an excellent add-pack that is more on par with a good synthetic, deals with soot/carbon well, and can be had for around $7/gallon.
2. Delvac 1 is a pure synthetic made by mobile/exxon (also a diesel oil)... It is made from Pure group 4(POA) base stocks, has an excellent add pack designed to deal witht he soot/carbon of a diesel engine. When you can find it- it is often sold for as little as $13/gallon.
3. Another aproach to reducing engine wear, is to use an oil that is high in Moly(friction modifier). Do an engine flush to clean some stuff out(possibly a seafoam treatment, or an Auto-RX run)... then start using Regular old Havoline. Believe it or not, regular dino havoline boasts some of the highest moly count in oils available. (high levels of moly in suspension, provide a microscopic layer between moving parts, that helps reduce friction/wear considerably) And havoline is one of the cheapest oils available.
4. To get the Moly benifits mentioned above in the oil of your choice, Valvoline offers an oil treatment in a little silver bottle that contains a very high concentration of Moly.
hope that opens up some more confusion for everyone!!! hehe (or helps someone reach a conclusion)
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