Do I have it all wrong?

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Jan 6, 2005
North Alabama
If Auto-RX cleans engines & synthetic oil "cleans" engines, would my following theory make sense?

Let's use my wife's 97 Expedition as an example. It ran on dino for it's entire life, until I switched to a 6:1 ratio QS semi-syn./MMO mix at 109k. I drained that mix out at 110k, & filled with Havoline synthetic. The next oil change will be at 115k.

So, if synthetic oil has a "cleaning" effect, would it make sense to fill the Expy with dino oil at 115k, for a few thousand miles as a "rinse"? Sort of like the Auto-RX principle? Or is my theory all wet?

Thanks in advance,

[ May 11, 2005, 03:43 PM: Message edited by: wavinwayne ]
Frank says not to use synth with an Rx treatment so that there are no ester conflicts with the type of ester in Rx and what ever ester is in the synth. I would guess a group III synth with no esters in it (if there are any) would also work with a rx treatment. Dan
I am not sure if synth oil actualy cleans an engine or maybe it just does not get it as dirty as dino does. Dan
I somewhat share Dan's take on it. My belief is that oil has only so much "holding potential" for "stuff". If you've got a sludged engine, any new oil is going to suspend some of that stuff. This detracts from the capacity for wiping up after itself to speak. Synthetics probably have some properties that make this liberation easier ..but probably they have no more holding capacity as far as amount ..but (probably) can do it longer in terms of time before they start creating more deposits from their own creation. HDEO's probably have an edge over PCMOs in this dept. Although surely filtration plays a decent role in this, I think that from a practical stand point that your oil mainly limits deposits. That is, the amount of "cleaning" that an oil can do will have more to do with the length the OCI then it will with which oil is used. Some may reach saturation earlier than others but can probably handle no more than just about any other oil (again HDEOs may have an advantage).
I noticed significate cleaning occurring when I did multiple oil changes on a BMW 320i.

Used the following oils over 7k.
ST 20W50
Pennzoil 15W40
Castrol HM 10W30
AAP 20W50
Maxlife 10W40

Yeah most of the intervals were short but there was a good amount of cleaning going on.

I think any ole decent dino if changed before 2K will do some cleaning.
People used to say that synthetic "cleans" so well - if you switch an old beater over to syn - all sorts of hunks and chunks will break off and kill the engine.....I suppose this could happen.

My real life observations have been that synthetic does clean when new at the expense of oil consumption.....then the consumption goes down a bit....then the engine only gets so clean on synthetic - even after 10's of thousands of miles. I don't believe synthetic cleans ring grooves worth a hoot.

The only cleaner I have actually seen work near the pistons is AutoRx.
The Grp III base oils have only fair solvency ratings & need an add for seal swell. The Havoline synthetic will have little effect on existing sludge or engine deposits.

IMHO, the potential for a PAO based synthetic to clean only comes from the PAO base oil's better flow & film characteristics which then allow the detergents and dispersants to perform their job.

Alan has a good point, multiple dino oil changes - HDEO is even better - over short, 1K intervals, will clean-up an engine, not as well as Auto-Rx, but definitely cleaner.
Only ester based synthetics have a significant cleaning effect. PAO is not very polar and has almost no solvency at all. Group III is in the same boat as PAO in terms of being non-polar and non solvent! You ester based fluids will clean butnot as well as Auto-Rx. Auto-Rx is designed to clean ester based lubes are designed to lube. If you ask an oil to clean it will have to scarifice a lot of it's lubricateing ability.

It is alot like strength versus endurance. Both are oposite copopnets of fitness. You can not have maximum endurance and maximum strength at the same time. Each one requires specilized training for adaptation to occur.Example Olympic weightlifters versus Olympic marathon runners. Like wise the chemistry for lubricateing and the chemistry for cleaning are totaly oposite of each other when maximized. Oils are their to lubricate and slow the engines accumulation of junk dureing that one oil change. Oils are not designed to clean all the junk from 109,000 miles of accumulation!! Auto-Rx is designed to clean the 109,000 miles of junk out of you engine with out disturbing the oils ability to lubricate!

If you want to see what a 110,000 mile vechile can fell like when it is clean do an Auto-Rx treatment.Buy the time you enough Redline or Motul to fill that crankcase up with ester based oil you could have done Auto-Rx saved money and had a cleaner engine!
I successfuly switched to M1 about 1 year ago in 2 of my cars with > 50K miles. Previously, I used only Dino and changed it every 3 months or 3K miles. In my '97 Camry, I had the oil pan gasket replaced (just before switching to M1), and I got to examine the entire lower end of the engine - it was clean everywhere! In my '00 Odyssey, I can see the valve springs and rocker through the oil-fill hole - once again, clean! However, using M1 in both of these cars surprised me that it darkened significantly within 8 weeks, so I changed it at 15 weeks. The second batch got dark also, but not as fast. I am now on my 3rd batch of M1 in both cars and it has stayed clear after 5 full months with no oil added. On the Camry, the part of the block inside the oil filter gasket area is definitely cleaner (that's all I can see on this engine), and the Odyssey valve train now looks factory new.

I know that M1 is a PAO, but there is something in it that cleans things, even if it wasn't "dirty" previously.

BTW, I agree with Steve S. that the key is not to let it get dirty in the first place! This is the strategy I am using with my '03 Civic - I switched it to M1 at the first oil change (4k miles) and am happy to see everything still clean.
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