Engine Flush when changing viscosities

[93z383lt1]

I'm going to change from 20w50 to 5w40, in addition the oil will be a year old after coming out of storage, should I use an engine oil flush? If so what kind do "we" like and for that matter when should you do an engine flush if at all?

 

[BrianWC]

Try a search for "oil flush." Most around here shy away from them. I like chemtool when I do do one but MMO and Seafoam are a bit gentler.

 

[Blake Sobiloff]

Don't waste your time, 93z383lt1, with an engine flush. Just give your vehicle a good run (20+ minutes) at highway speeds, then dump the old oil and refill with your new oil. The highway run should help free up some of the surface rust and get it out of the system.

 

[John Hilmer]

I agree with Brian & Blake, stay away from the harsh stuff.

If I were going to do anything other than Blake's method I might add some LC-20 or MMO for the warm-up run just for grins & giggles. John

 

[Shannow]

Check your sump carefully before doing anything like that.

Both my 4WDs have a small "sump" ahead of the front differential that won't drain, and hold maybe 0.5 to 1 litre.

That's a lot of solvent laden oil to be left in an engine

 

[Big Jim]

I would not bother with a flush unless you know that you have a sludge build up. Taking an engine out of storage doesn't create the need for a flush and neither does changing viscosity. Just get the oil hot and dump it.

Although I believe there is a strong element of snake oil in the engine flush machines, I have been around them enough to be able to say that they do a good job. The only problem is that 98% of the engines that get an engine oil flush didn't need them. When needed, I like the Bilstein machine.

 

[Ken2]

If you wish, drain the cold 20W-50 as best it will drain, refill with cheap 10w30 or something like that, run until hot, then drain and add you 5W-40.


Ken

 

[Alcibiades]

If you think the engine needs some cleaning, try an Auto-Rx cycle. (This will take some time: 1,500 miles for the cleaning phase and 2,000 for the rinse, both using a good non-synthetic oil.) Otherwise, just get it nice and hot and then dump it. Depending on the placements of your drain plug and oil pan, you might get more out by putting either the front or rear end up on jack stands while draining. I have found that to be the case with both of my cars.

 

[toocrazy2yoo]

Engine flush just to change viscosity?

NOW things are going a bit far...

Just change the oil, and it might be a good idea not to put MMO in the crankcase. Stuff contains chlorinated solvents, isn't it? Ok in the gas, but not the oil, maybe?

Kinda like, DURALUBE (which I wouldn't put in the gas or oil)?