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Triumph TR6 - Oil Pressure

Anybody have the experience of Synthetic oil(15w50) causing the oil pressure to drop considerably i.e. 60 hot to 40 hot,@(2500 rpm), 35 to <20 at idle (900rpm)?
If engine wear & tear what is most likely cause. Main bearings, oil pump, oil pressure valve or other? I have no problem with doing the job however, just want to do it once! The car does not smoke or spill oil so I am concerned.
Thanks All
B.R. Horne

Yes, that will happen if you change to straight synthetic. You will likely find (more) leaks as well.
The reason is that synthetic oils are thinner, for better flow on start-up, especially in cold weather. Since our cars generally have looser bearing clearances and are not used in winter the benefits of synthetic oils are reduced.
You could try a blend of 1 or 2 litres of synthetic with mostly conventional oil, this should restore your earlier pressure readings and may give some benefit in terms of friction reduction and reduced drainback.
No doubt others have additional information (know more than I do!)
Simon.
Simon Rasmussen

B.R. I too had a similar concern re synthetic oils. I repaced the Castrol 20-50 that I ran in my motorhome with Castrol 5-50 synthetic. Left on holidays and after the first 200 miles was looking for a quick lube shop to change out. My normal hot opperating presure was visibly lower. However, when I got into the mountains and the old Ford had to work, to the point where my fan actually kicked in, my oil presure climbed higher than it had been with the 20-50. I presumed that the synthetic needed a little more heat to affect the viscosity. Seems to run well with the synthetic.
Brian
B. Towne

My opinion on syn oils for our old cars is that it is more important to change the oil frequently given their limited use. Given this, syn is not a cost effective solution (on modern cars with extended drains, it's a whole different story). What you may find beneficial is an oil with a heavy duty addivtive package, like any oil designated for diesel engines. My personal mix in my six is 50:50 Rotella 10W-40 and Castrol 20W-50. Mobil Delvac is also a good choice for this.

Rick O.
72 TR6
Rick Orthen

Rick,

I also use Castrol 20W-50, but am curious why you mix it with the Rotella brand? I'm not familiar with it.

Jim
Jim Vandenberg

Rotella is a diesel engine oil and is found in any Wal Mart in a blue gallon container. I use it to get the additional additives that gasoline engine oils do not have. A long time ago I made the mistake of visiting an oil/filter website (www.bobistheoilguy.com) and got an education on the subject. It was there that I learned of the benefits of using diesel engine oil in classic cars.

Rick O.
72 TR6
Rick Orthen



Synthetic oil. Sounds marvellous doesn't it? Especially having spent loads of money bringing a car up to race spec.

I started racing my TR6 a few years back. The race specialists who supplied the modified parts and built the engine highly recommended using synthetic oil as it drastically improves the engines ability to rev.

And it was true. The car revved like one of those Japanese rice burners. Of course those big old cast iron bearings simply threw the 'cooking oil' off and I blew three engines in one season. Kept the race specialist' engine builder busy and my pocket empty.

I learned my lesson the expensive way. The current engine runs on 20/50 as I couldn't afford another rebuild. So in my opinion stick to castrol GTX.
Barry Ricketts

Barry - Was the syn you used a lower viscosity than the 20/50? My guess it was.

The viscosity ratings of "multi-vis" oils are standardized at 0C and 100C. Doesn't matter if it's syn or dino - if the oils have the same "rating", the viscosity will be in the same limits. From what I've learned a syn oil will maintain a higher viscosity above the 100C spec, while the viscosity of dino oils will droop. That's especially true with longer run times or high shear conditions - the long chain side branches of the dino molecules tend to break off, which lowers the viscosity and breaks down the oil.

So, I would never recommend that one pop in a 5w-40 syn in place of a 15W-50 dino to take advantage of the lower viscosity. Engines may blow. But a 15W-50 syn should always out-perform a 15W-50 dino.

BB
Brent B

This thread was discussed between 24/09/2004 and 04/10/2004

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