Oil Pressure

[1950MercMan]

Yes Rotorwrench, I saw the 10W for below freezing temps. My manual also said that for temps that persists below -10 degrees to add 1 pint of kerosene to 4 1/2 quarts of 10W. Interesting.
Thank goodness for multi-viscosity oil

 

[rotorwrench]

On a long drive, the kerosene will evaporate out but it will thin it for a short while. Big round motored aircraft used to dilute with avgas for winter starting but they had a special design oil tank to do that. It put the fuel directly in a smaller semi-contained area in the oil pickup section in the bottom of the tank. Avgas or mogas would evaporate quicker than kerosene.

 

[JSeery]

Yes Rotorwrench, I saw the 10W for below freezing temps. My manual also said that for temps that persists below -10 degrees to add 1 pint of kerosene to 4 1/2 quarts of 10W. Interesting.
Thank goodness for multi-viscosity oil

May just be being picky, but are you misusing the "w"? Flathead would have used straight SAE viscosity ratings originally. The "w" stands for winter, and relates the the temperature the viscosity is determined. Not sure when muli-viscosity ratings became common.

See correction in post below.

 

[1950MercMan]

Hi JSeery,

I don't know. The manual seems to list it both ways, so I don't know if there is a difference or if it is using the terms interchangeably for the same type of oil. I will type the relevant sentences from the manual and see what you think.

"In warm weather use S.A.E. No. 20 or 20W in your Mercury.

In below freezing weather use S.A.E. No. 10 or 10W

If temperatures below -10 degrees F persist, use 1 pint of kerosene with 4 1/2 quarts of No. 10 or 10W oil"

 

[JSeery]

Guess that is correct, you just don't normally see 10W listed separately. It basically means an oil with an SAE 10W rating has the same viscosity as SAE 10 at that temperature. You normally see it as 10W-30 say, which means the oil has the same viscosity as SAE 10 oil would at the lower temperature and the viscosity of SAE 30 at the higher temperature.

A lot of people seem to believe that "W" stands for weight, got myself confused on this one!

 

[tubman]

I think that all this discussion about "now vs. then" is moot. Today's oils are so superior to what was available when these cars were new that comparisons are hard to make. Most of the oil available back in those days was non-detergent. I don't think I'm the only one on here that believes detergent oil is a desirable upgrade to these old engines. With the "multi-viscosity" oils currently available, I don't think you can be hurt if at least one of the numbers match what the old manuals say.

When I was racing the (very expensive) early hemi in my dirt car, all of the "old-timers" told me that "them hemi's need lots of oil". I ended up with a modified sump, an oil cooler, dual filters, and a 14 quart capacity. We used Mobil-1 20w-50, because any oil sold in those days with a "50" in the weight had over 1300 PPM of zinc. When my racing days were done, I ended up with 3 cases of Mobil-1 20W-50. Being the cheap ******* that I am, I used it ion my '51 Ford and '67 Corvette until it was all used up. The oil pressure gauges in both cars registered the same with that oil as they do now with 10W-30. I have to believe that the relief springs in those oil pumps were functioning properly.

In my opinion, if you have a stock or near stock flathead, the current oil is so much better than that available back in the day that you don't need to worry. If today's oils aren't good enough, you probably need a rebuild.

 

[1950MercMan]

Well, I no longer have any faith in electrical oil pressure sending units. I had ordered another on the chance that the one I had was faulty. The new one gave a completely different reading which was even lower than the one I originally had. I will be sticking with the mechanical unit which I believe gave an accurate reading.

 

[AnthonyG]

Good logic on the Mech. being more accurate & reliable. Consider, I have a Mech. Mounted in the engine compartment & a electric mounted under the dash, my logic was that I have a very nice cloth interior & have had a mechanical leak & feed hose break & make a mess in the interior. I personally use an electric Stewart Warner M-82756 inside with good results & when if that gauge gives me a symptom I can verify with the Mech. on the engine. Also if it’s been covered I apologize, many times it’s the sending unit not the gauge that goes bad.

 

[supereal]

If you have the typical oil filter for earlier flatheads, check the lower fitting to see if it has been modified. That fitting should have an outlet of about 1/16 inch diameter. If the fitting has been replaced or drilled out, your oil pressure will be reduced as it bypasses the oil flow thru the block. By starving the pressure, the bearings are at risk.

 

[1950MercMan]

Thanks AnthonyG for the idea of mounting the mech in the engine bay. My car is all original and I would like to keep that look inside and out, not to mention the chance of a leak into the interior.

I will definitely check that outlet supereal.

I thank everyone for their input and information.

 

[drolston]

Well, I no longer have any faith in electrical oil pressure sending units. I had ordered another on the chance that the one I had was faulty. The new one gave a completely different reading which was even lower than the one I originally had. I will be sticking with the mechanical unit which I believe gave an accurate reading.

The replacement type oil pressure sender indicated approximately correct for four years, and then started showing 20 psi with the engine off. Bought another repo and zero is back to zero. For now. I don't much care how accurate the pressure reading is underway, as long as zero shows zero.

The oil sender is one of the hardest things to access, even with the floorboard out. When I put the engine back in after overhaul, I put a 3" brass nipple and a female to to female adaptor in. Makes the sender swap much easier.

 

[AnthonyG]

I tried same on my ‘35, thought a great idea for access but it interfered w the throttle pivot linkage. I have the oil filter canister now so I mounted on the line feeding it before the 1/16” restrictor. If u go with the bypass filter it’s makes access simple.