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MG MGA - Oil Observation

When the ZDDP additive issue came to light, I searched and found Mobil 1 V-Twin 20-50 synthetic oil and switched over to it. With the availability of Classic 20w 50 (a non-synthetic oil) through Moss, I switched back. Driving with the former oil, on a 50 degree day the running temp stayed down around 160 deg. F (185 deg. thermostat) Now that I'm running the non-synthetic, the temperature under similar outside temperature stays somewhere between 185 and 190 degrees F.
D Sjostrom

That's interesting as you seem to say that your synthetic oil keeps the engine cooler - this links with the oil cooler thread and Steve's other oil question.
Cam Cunningham

Doug,

That seems strange. The thermostat should set the minimum operating temperature of the engine. If the thermostat is a 185F unit I would expect the temp. to always be at least 185F. Maybe at one point the thermostat was stuck open causing the over cooling to 160F.

Dave
David Ahrendt

David, it doesn't seem to work like that.

I have had overcooling problems with my car since I fitted the Judson. On a cold day, unless I cover half the radiator with cardboard (really must get that rad blind fitted), the car runs at 50C regardless of road or traffic or incline. With half (or more) covered, it runs at 72C. That is with a 80C thermostat fitted. It was the same with a 70C and 75C thermostat. I have an oilstat to fit in the hope of getting an effect, but I only do this because I got a bargain on ebay. If I also cover up the oil cooler, it makes a minimal (1-2C) difference on the gauge.

I know it's not the gauge - with 90% rad covered going up a steep mountain pass on a 0C day, the temp climbed to 95C. I have also tested the gauge in boiling water - 100C spot on.

For the metrically challenged, 100C = 212F, 72C = 161C, 50C =122F, 2C difference = roughly 4F

And I am using mineral oil too, better stay away from the synthetic stuff!
dominic clancy

While it's still cool here in N.E., I'm going to switch back to confirm.
D Sjostrom

Confirmed!
Changed out the oil back to Mobil 1 V Twin 20w 50 SG rated Motorcycle Oil. Temperature on a hard run at 55 degrees F outside never exceeded 180F Only an extended garage idle brought the temp up to 185F. The oil pressures between the two oil types were the same, 70 psi at speed and 60 psi at idle, which would tend to indicate viscosity between the two types remained similar. Reduced heat from friction is the only explanation that makes sense.
Doug
D Sjostrom

Interesting Doug. So, which will you go with long term?
M. D.

Mobil 1,
Especially since I'll be hauling a trailer to GT 33.
Doug
D Sjostrom

This thread was discussed between 03/05/2008 and 06/05/2008

MG MGA index

This thread is from the archive. The Live MG MGA BBS is active now.