Back in August of 2023 I bought a 91 chevy S10 as a second vehicle. It has about 150,000 miles. After I got it home I immediately changed the oil because the oil that came with the truck was black as coal. As of now, six months later I have put a total of a little over 700 miles on this truck and the oil is very dark already. I’m considering doing an engine flush. If I follow the instructions, is this something I really want to do on a high mileage engine? Your thoughts and opinions. Thanks.
I have never seen that as recomended. Some of the deposits at that are may be a good thing. Personal experience from way back, I put a can of engine flush in a truck with 200k, couple weeks later the head gasket let go. Then most my car friends gave it to me for flushing. Should have just left it alone and keep changing the oil. Take it for what it is.
As a professional auto tech for the last 30 years, don't do it. Those flush products are basiclly kerosene. All the sludge in the engine will get loosened up and end up in the oil pan where in turn will plug up the oil pump pick up screen then you lose oil pressure. Stick with more frequent oil changes.
What kind of oil filter u using?
AC DelcoOriginally Posted by yatesville88fan
Thank you sir. Based on your experience and knowledge I will not be using an engine flush. Frequent oil changes are cheaper than a new engine.
I think the black oil is gonna be permanent. My guess is you could change it at 500-1000 miles a couple times and the results will be negligible. Every vehicle I have owned from new to high mileage has black oil fairly quickly. I would be leery of flushing that crud around as previously noted. I had a 350 chevy engine with 300K on it that I used Pennzoil in. It had it's share of sludge in it but it ran fine. I changed oil in that vehicle every 3000 miles.
GETFISHED !!!
Change your oil every 3000 miles, had a brand new 88 S-15 Jimmy with a 4.3, changed the oil every 5000 km (3106 miles) and when I sold it, had 385,000 (239,000 miles), ran great and never burned oil.
Aren’t most sludges stored up top under the valve covers? Might be able to pull the covers and remove sludge deposits with a pick and vacuum being careful not to let any fall down the oil return passages.
'94 Charger Foxfire 180VF '96 Suzuki DT150S BASS
That’s been my experience back in the day when I had my head under a vehicle hood daily. My family has had a garage since the 80’s and I’ve personally worked on hundreds of engines. Once motors have some age, the engine/cooling flushes seem to rapidly deteriorate gaskets/seals. I’ve never recommended them. As far as oil flushes, a quart of automatic tranny fluid circulating in an already warm engine for 10-15 min just before each oil change will help keep it nicely clean. It’s a detergent, yet won’t deteriorate gaskets. Done it for years.
Last edited by WVBullet; 02-11-2024 at 01:51 PM.
2008 BULLET 21XD 2007 Merc 300xs
Don't do a flush, just use 15w40 diesel motor oil. It has more detergents in it that will help clean up all the soot.
Flushed a 1980 Ford 302. After flushing the rods went to knocking. Had to rebuild that engine.
I've done cylinder head rebuilds back in the mid 70's. Many came in loaded with a sludge film all around inside the valve covers. In this case it may be possible to look inside the oil fill on the valve cover and see if it's clean or gunked up.
Back in the 80’s, I noticed different oils would sludge up way more than others. Some not at all. Now in the cooling system, I’m not a fan of engine flushing for the cooling system. I will flush radiators to extend life. I’ve seen so many systems that looked like they used mud hole water. The stop leak additives created the most gunk in the system. I’ve known people to just keep adding stop leak and before long, almost total plugging.
2008 BULLET 21XD 2007 Merc 300xs
A friend did that years ago and the motor started leaking in places he didn't know there were places. Just change the oil more frequently.
Back in the 70's we also used tranny fluid to clean out a engine.
There is always the slogan, if it ain't broke. Don't fix it!
I'm guessing you got a killer deal buying it in this condition.
Mixing oil brands might have something to do with continued black oil after every oil change as the detergents in the oil you are using just might be slowly cleaning away at the sludge that's there now.
Personally I would get a compression test to know the health of the engine prior to dumping a ton of time and money into an old light duty truck. My two cent's, take it for what it's worth.
Last edited by Delta Bass Fool; 02-11-2024 at 06:24 PM.
'94 Charger Foxfire 180VF '96 Suzuki DT150S BASS
Just keep changing both the oil and a good filter. It will clean up.
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Same with transmission flushes in my opinion.
We did too, I was a tech in 79,80, and the owner of the garage did this all the time with dirty engines. Also poured it slowly down the carb (before the tune up) while reving the engine to help clean the valves and combustion chamber. Don't know if it worked but it created a heck of a smoke show. We also did this with water, primarily on little old lady's cars that never saw more than 1/2 throttle. The theory was that the sudden change in temp from the cold water in the chamber would cause the built up carbon to break loose. You had to give it quite a bit of throttle to keep it running and there would be a lot of stuff coming from the exhaust.
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