Wednesday, January 27, 2010

Engine Flush

I just returned to the house from a visit to Bixby to have the oil changed in my 2005 Dodge Pickup. After the technician that did the oil change had finished the oil change he came over to me and told me that now that my truck was 5 years old and had nearly 50,000 miles on it that I needed on my next oil change to have them also do an engine flush. I asked him what that involved and he said an injun flush was when they had their technician who was a Cherokee Indian perform the oil change service. (not really, I just made that up) What he really said was that they used a special machine to force cleaning agents back through the engine to get all the gunk and grime out of the engine and that all manufacturers recommeded that the procedure be done at around 30,000 miles. I checked my manual and it doesn't say anything about engine flushes. I was just wondering if any of the rest of you have had any experiences with engine flushes?


At January 27, 2010 at 11:33 AM , Anonymous Anonymous said...

I have had no experience with engine flushes, but I have had plenty of experience with engine lube places telling me I had filthy filters, nicked hoses, belts about to break, automatic fluid that needed to be exchanged, breaks that were on the edge of failing, just about any service that is ever due on any car is overdue on my car.

At January 27, 2010 at 4:18 PM , Blogger Glen Lazalier said...

Colin, the only "flushes" that should be performed on an automobile are the cooling system and, possibly, the automatic transmission. If you use a detergent oil (and almost all of them now are detergents) there is never a need to "flush" the engine itself. In the old days before detergent oils, I would drain the crankcase, refill it with kerosine, and run the engine for a minute or two to break the sludge loose. With today's tight tolerance engines that would probably be disastrous. So, just change your detergent oil often and use a synthetic if you want to extend the time between changes al little.

Even considering the two flushes that may be done, I have had good success with cooling systems that were not flushed for several years and up to 200,000 miles. There is a risk in flushing an automatic transmission so I usually just drain and refill it every 50,000 miles or so. That's not what the manuals say to do, but it works for me and my cars. When an automatic transmission is drained and refilled it replaces about 80% of the fluid. A flush, properly done, can do a 100% exchange but doing it properly requires some special equipment. Many shops will just try to match the outflow from the transmission piping with new fluid they are putting in with the engine (and transmission pump) running but this is hard to do precisely while not starving parts of the transmission. A proper set of equipment maintains a positive pressure on the input fluid and assures no starvation.

Bottom line--I would never, never "flush" an engine, never flush an automatic transmission unless (1) the proper equipment was used and (2) the transmission had bee grossly contaminated (like being underwater for a long time). Flushing a cooling system probably does no harm but a simple drain and replace the coolant is all that is really needed.

At January 27, 2010 at 4:34 PM , Blogger colin said...

Thanks Bob and Glen. I suspected such was the case. I have had my oil changed at this place before and they never offered to do an "engine flush" before so I expect they have got themselves a new machine lately and are trying to pay for it with suckers like me. Thanks again and no engine flushes for me never ever never.


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