Flushing Oils

I thought this subject might deserve its own thread.

I was reading the thread about “SW-20 vs SW-30” oils and clicked the “Car Bibles” link given by ‘The Same Mountainbike’.

I found this when reading about oil -

Flushing oils

These are special compound oils that are very, very thin. They almost have the consistency of tap water when cold as well as hot. Typically they are 0W/20 oils. Don’t ever drive with these oils in your engine - it won’t last. (Caveat : some hybrid vehicles now require 0W20, so if you’re a hybrid driver, check your owner’s manual). Their purpose is for cleaning out all the gunk which builds up inside an engine. Note that Mobil1 0W40 is okay, because the ‘40’ denotes that it’s actually thick enough at temperature to work. 0W20 just doesn’t get that viscous”

It appears that the author is of the opinion that 0W20 oil isn’t even good for a hybrid.

Am I misinterpreting the above?

If your vehicle requires 0W20 oil, and you choose to use a different weight because someone on a website said so, how do you think the factory reps will view it when considering your new car warranty?

Many new cars are running fine today on 0W20 oil. That weight may be driven by fuel economy standards, but is there any evidence of shortened engine life from it?

I understand your point, Joe, and I agree.

But I’m just the messenger.

I’m curious as to what others think of the author’s viewpoint on so-called ‘flushing oils’ and the long term affects they think the oil might have on a hybrid engine - assuming the author is correct - or whether or not people agree with the author.


Most car engines are designed to run on W30 and W40 oils. Running W20 in such engines will lead to premature failure.

However, some engines are being designed to use W20 oils. With these engines, W20 will not hurt them at all. But, the flushing oils typically contain a lot more detergents and much fewer anti-wear agents than you’d see in motor oil specified for the car in the owner’s manual. In that respect, they would still not be desirable for regular use in driving the car.

I think that a very relevant question would be:

What specifically are the qualifications of the author of the oil information on the Car Bibles site?

As we know, anyone can pontificate on the internet.
A lot of genuinely authoritative information is available on the web.
Unfortunately, there is also a HUGE amount of misinformation.

Below is what I copied from the top of the oil page on the Car Bibles site:

“I am a pro-car, pro-motorbike petrolhead into basic maintenance. This site is self-published to spread my knowledge. By reading these pages, you agree to indemnify, defend and hold harmless the author, any sponsors and/or site providers against any and all claims, damages, costs or other expenses that arise directly or indirectly from you fiddling with your vehicle as a result of what you read here. If you hurt your vehicle or yourself, don’t blame me.”

I don’t see anything listing this guy’s qualifications as a scientist, a certified mechanic, or even someone who has practical experience in the petroleum industry. Do you really think that his opinion regarding 0W-20 motor oil carries as much authority as the engineers who designed the engines that are supposed to use this oil?

When I read the section on flushing oils in the “Car Bibles” site, it’s not clear if there’s a distinction being made between:

  • "0w20 oils specifically designed for flushing your engine"
  • “0w20 oils designed for normal engine lubrication and operation”

It almost sounds like the author is saying 0w20 oils designed for normal engine lubrication and operation should never ever be used (because of their flushing behavior and water-like consistency. If that’s true, then I need to question that logic. Many new vehicles today (hybrid and non-hybrid) specify 0w20 oils. If the 0w20 oils were truly flawed, where is the problem?

PS: I agree with BustedKnuckles that 0w20 oils should not be used in older vehicles designed for heavier oils.

The ONLY people who need “Flushing Oil” (whatever that is) are those who subscribe to 8000-10,000 mile oil change intervals. If you change your oil every 3000-5000 miles, there will be no accumulated gunk to flush out.

These oil lunatics are infiltrating this forum when they used to content themselves on the bobistheoilguy site…Too Bad…

Anyone here ever seen a quart of ‘flushing oil’? Not me. I’ve seen things like Rislone.

Very few cars spec a 40 weight only anymore, the only ones I can think of would be some of the BMW M cars. But for the vast majority of cars made in the last 10 years or so 5W-20 is by far the most common recommendation.

Why do you want to use an oil change regiment different than what is listed in the owner’s manual?

…or even an oil change battalion, for that matter