MMO in crankcase - Topping off question

[KCJeep]

A question for those of you who use MMO in the crankcase.

I was recently running some Delo 15w40 in my Jeep 4.0, after about 1000 miles I noticed a definite "knock" I'd not heard before even when the engine was warm. I wondered if the Delo may have been too thick for my particular 4.0 (I know many guys run it)so I drained out a quart of the Delo and added a qt of MMO to thin it. You guessed it the knock instantly disappeared. So now I know my Jeep doesn't like 15w40 so it seems.

Well that was about 500 miles ago so now some of the MMO has burned off, I'm needing a bit of a top off. Do you guys top back off with MMO when it burns off or start adding oil back in? I don't want too much MMO but I was curious as to what you do when it's burned off.

Thanks!

 

[Oregoonian]

Need more info....

What vehicle?... mileage...Intended OCI?
Where do you live in the USA?
Driving habits?
What weight oil does the manufacture (manuel) recommend?

 

[zyxelenator]

After reading euro versions of BITOG I'm pretty sure that weight of oil is not the case. Guys overseas mainly run 40 and 50 grade oils, same engines that are imported to US and run on 30 weight, and engines much smaller than yours.
Which filter did you put on?

 

[spasm3]

I would be checking out the filter!

 

[mongo161]

IMO....If the Delo 15w40 seems too heavy...and your vehicle is not a diesel and a gasoline engine....you can always thin it out a bit with some lighter conventional or synthetic PCMO.

I do it all the time.....with gasoline engines and fleet motor oils.

 

[NYSteve]

Does MMO regularly burn off?

 

[demarpaint]

Originally Posted By: NYSteve
Does MMO regularly burn off?


In some applications it does, some it doesn't, at least from my experiences. I suggest to anyone using MMO in the oil to keep an eye on the oil level, top up as needed and don't let MMO exceed 20% of the crankcase capacity. HTH

 

[KCJeep]

It's a Purolator Classic filter, oversized, and I think I'm done with the oversize filters as well I'll likely go back to the standard sized PureOne I used previously.

I reckon I'll continue to top off with 10w30 then if needed as I'm close to 20% MMO already.

 

[mechtech2]

Of course it will burn and leak more -MMO is very thin.
I'd top up with engine oil. Lots of MMO in the crankcase is something I shy away from.
Was this a tick or a knock? I can't see MO fixing a knock - only making it worse.

 

[KCJeep]

It was a knock all right, it hadn't been there before and it hasn't been there since I added the MMO. Makes me think it was simply too thick for my engine.

I've only had this particular Jeep about 5 months, I've caught up and done all the maintenance but I have no idea as to it's OCI history. From what I've seen through the fill hole it may have been neglected. I wonder if some sludge plus the thicker oil was enough to cause the knock due to poor flow.

I've got it on a good cleaning schedule so it should come back fine, but I'll not be dumping thick oil in it anytime soon. I'll be returning to Rotella 10w30 and a standard filter which worked very well before.

 

[LeakySeals]

Whats missing is the age and the miles on the vehicle. That will answer whether 15w40 is causing problems, and should be drained immediately. MMO is no substitution for motor oil.

 

[zyxelenator]

No more than 1 q of MMO should be used during one OCI, at least it is not recommended. If engine sludged up, 15w40 oil is not your friend. 5-30 or even 5-20 if you got cold winters.