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MG TD TF 1500 - Dirty Oil

What would cause the motor oil to turn black after a couple of hundred miles?
Is this normal?
Mort 50TD (1851) Mobius

My experience with anitque cars has indicated to me that there is a lot of yucky sludge in the engine when this occurs after a short time. Mike
MW Davis

Take a peek at the plugs, Mort. Sooty plugs indicate a rich mix - will dirty up the engine oil in a hurry. Just another thing to consider. Dan
Dan Craig

What new oil did you use? Maybe the new oil has more additives to keep dirt floating. Typically an oil for Diesel engines would have that.

Otherwise I agree with the other remarks about old dirt and rich mixture.
Willem vd Veer

Is this a newly rebuilt motor with the first oil change?
Dallas Congleton

I have no history on the engine. I bought the car 1-1/2 years ago. I removed the head for a blown head gasket about 6 months ago. The amount of wear observed where we could see, indicated a recent rebuild.
A few months ago I added the spin off oil filter adapter and changed the oil for the first time. I then changed it again after a couple of hundred miles. Both times using a 10W30 Castrol GTX oil. Just now, after a couple of hundred more miles I switched to Valvoline VR1. The Castrol I took out was black with low mileage. 1 & 2 plugs were nice and tan, 3 & 4 were a little black. (supercharger, hence one carb?????)
Mort 50TD (1851) Mobius

These engines like a heavier oil, such as the VR1 20W50. I've never considered whether a lighter oil would contribute to faster dirt build up, but I imagine it could. For the record, I've never tried 10W30 in one, but did use straight 30 for the break-in of my XPAG.

What weight did you put in this time?

Dave Braun

I switched to Valvoline VR1.
Mort 50TD (1851) Mobius

Virtually all early MG's call for 20W50, unless you live in an extreme climate...
Valvoline VR1 is an excellent , high ZDDP oil...
It is possible, that the supercharger is causing a bit of "blow-by", due to higher cylinder pressures, forcing unburned hydrocarbons past the rings....
You can check your compression, which would show some lower numbers, if the rings are a little worn....
Just curious...
Do you see black smoke when you first start the car, cold? (You will need an observer to tell)...
That can indicate worn guides, which can lead to dirty oil, as well.
E.B. Wesson

Also note whether or not you see a puff of white smoke as you let your foot off the engine, let it slow down and then step down on the gas again. This is a pritty sensitive test.

Jim B.
JA Benjamin

Mort, VR1 is available in 20w50, straight 50, 10w30, straight 30, straight 40, and straight 60. Which one did you purchase?

Dave Braun

Dave ... 20W50 VR1

Ed, Jim,....The car is down waiting for a set of vanes for the supercharger. When I start it next week I will report my observations at the tail pipe.

Mort 50TD (1851) Mobius

The upside of dirty oil is that you know the oil's detergents are doing their job. Personally I wouldn't worry too much about it. Just do your scheduled oil changes and drive the car regularly.
Steve S

BE VERY CAREFULL, Oil formulas have changed with time and the Public Relations folks have been busy.

VR-1 now comes in two forms now, one is listed as type SM which meets the ZDDP reduction to well below the needs for flat tappet engines
and the synthetic blend which lists as SL, which marginally meets our needs.

Neither will list the actual Zinc content.

I know of at least one MG that has used the SM VR-1 that has has his cam DESTROYED in 12,000 miles

Do not depend on advice based on articles from 2 or more years ago

Don Harmer

May have something to do with the flooding/burping carb? That may be dumping gas into the cylinders, etc.
George Butz

I read your posting with interest. I clicked my way through the Valvoline web site to their discussion on the VR1 group or what they call their racing oils.

VR1 Racing Oil (VR1)
VR1 racing motor oil provides true race-level protection with an anti-foam system effective against extreme stress.

Valvoline® Specialty Racing Oil ("Not Street Legal")
Optimized for track-use, specialty racing oil provides increased horsepower and extreme wear protection.

Valvoline® Racing Synthetic (VR1) Motor Oil
Advanced racing synthetic motor oil is proven to maximize horsepower during demanding driving conditions.

From there I went to the first product(VR1 Racing Oil (VR1)) and onto the FAQ titled "What solutions does Valvoline offer to the zinc issue?" The answers are at this link. I found it informative. They do list the percentages in answer number 6. The link for the answers is:

The VR1 Racing Oil (VR1)has .13% zinc and .12% phosphorus.

Mort 50TD (1851) Mobius

Good point Don and the issue of the reduction of zinc in motor oil for flat tappet cams is only going to get worse.

I have read in the archives everyone is a big fan of Red Line MTL-90 for the transmission and 75w90 for the rear axle. What about the 20w50 Red Line oil for the engine? Is it because the cost? They list the zinc and phosphorus content %WT and it's loaded with it.

I've been Red Line products in my Harleys for years with absolutely no issues at all. Yes, I know... it's not a TD or TF but it is still an engine and believe me when I say that my bike gets real hot idling in hot summer traffic and I ride it like I stole it. I buy my oil from Racer Parts Wholesale.

What concerns me is I read about people who use motor oil they been using for a long time because their mechanic recommended it 25 years ago but the formulations have changed to meet SAE requirements for the reduction of zinc to protect catalytic converters in today's automobiles. Reduction of zinc is good for catalytic converters but a death sentence for our little flat tappet engines.

It also concerns me that people adding "STP stuff" to cheap motor oil to meet the zinc requirements. Are you 100% sure what your pouring into your TD TF engine that you spent years restoring is really protecting your engine? What are you basing your conclusions this is "ok" for your car? Or are we going to take the chance like Don's friend camshaft was destroyed in 12,000 miles? 12K is really not a lot of miles... Wow!

The zinc and what oil to use debate is never going to really end. I strongly recommend when you change your oil next time is to have the oil analyzed. See for yourself if your oil and if your adding stuff with the cheap oil is really measuring up. I use Blackstone Labs and they will send you free sample bottles and the testing is about 25 bucks. You will also see how the metals are wearing and if there is any contamination in the oil as warning signs there may be some mechanical failure somewhere that needs to be addressed. Any by sampling the oil, you will know if you extend your oil changes. The cost of a bottle of Red Line 20w50 synthetic will pay for itself by extending the oil change interval.

Here is a copy of my lab report for my FLH. I used Royal Purple 20W50 in the spring because when I changed my oil at my friends shop, I forgot to bring my Red Line so we went to the shop down the street and got Royal Purple. I changed my oil for summer riding to 20w60 for extra protection with higher viscosity and higher flashpoint which explains the low mileage. Still, you can see how much zinc and phosphorus is packed in the oil and no noticeable wear to the internals of the engine.

Red Line 20w50 is going in my TF when I finally get it done.



Frank Cronin

This thread was discussed between 05/04/2012 and 07/04/2012

MG TD TF 1500 index

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