I posted this in another forum, but it needs to be here, I suppose. I have a question about my oil pressure in my 1972 F-100. I have the stock gauge, so I can't give you numbers, and I don't know for sure if the gauge and sender work exactly as they should. The engine is not original to the truck. It's a 351W and I don't know the history. I'm running Castrol 10W-30 with an el-Cheapo oil filter (for now). The gauge appears to be functioning correctly. When I start the truck, the gauge goes to the middle. If I run the truck down the Interstate at 70-75 mph, the gauge drops to just above the lower end of the "Normal" range. When I get back on a two-lane at a slower pace, it rises back up. It seems I read on here somewhere that the cheapo filters could cause this. My plan is to use the correct FL-1A at the next oil change. What else can I do to maintain the oil pressure for now? A rebuild may be in this engine's future, but it won't be anytime soon.

Thanks for the help! I really do appreciate it!!

 

Did this problem arise right after installing the el-cheapo oil filter. If so, or you suspect the el-cheapo oil filter has clogged up, why not just replace it with the specified Motorcraft oil filter & see how it goes???? Won't cost over $4 at the most to find out, less than $3 if you use online discount codes for Advance Auto.
Or stay off the interstate, or if you operate there, drive the speed limit & see how it goes.
Is your engine temp in the normal range, especially when running 70-75 mph on the interstate????

 

pawpaw, thanks for the reply!!

I guess I needed to offer a little more info. I just bought the truck, on Memorial Day, to be exact. It set in the driveway a few days until I could get the title settled. Since then, for about a month now, I have driven it to work everyday, about 14 miles one way. I had the oil changed after about the 4th or 5th day of driving, just so I would have a reference point. The place I took it to used the Castrol oil and the generic filter. I didn't really notice if this phenomenon existed before the oil change or not. At the next oil change, I'll shall un-do these mistakes. I seem to remember reading about the generic filters somewhere, maybe even in this forum. For now, I would be interested in suggestions as to what I can do to minimize the problem, but mainly I guess I'd really like recommendations about types, brands, and/or weights of oil that might be better for my situation. Or, any other similar advice would be good. The speed limit on my part of the big road is 70mph, so I am not a heinous law-breaker behind the wheel. And, the temperature gauge stays right in the same place regardless of which type of road I take, or how fast I have tried to go (so far). If the day comes when that sucker won't do 75 on the open highway, then it'll be time for a rebuild!!

Again thanks for the help!!

 

OK, good feedback. So the engine temp stays in the normal range at speed. 10W-30 is ok for summer, but 5W-30 would be better for cold winter starts you'll have in the mountains, as it'll flow quicker at lower temps to do a lube job on the bottom & top end faster & being less vicious when cold, it'll make it easier on the battery & starter motor turning this puppy over when cold.

Seeing as how you didn't perform the oil & filter change, with it on level ground, pull the crankcase dipstick to check the oil fill level, they may have over filled the sump & if so, the crank shaft may be dipping into the oil & aerating it at speed. The oil pump won't appreciate trying to pump frothy oil & the engine bearings won't appreciate being lubed by it either. If its been over filled, use a piece of hose longer than the dipstick, attached to a hand soap pump syphon tube & thread the loose end down the dip stick tube & pump enough oil out to get the level in the cross hatch area.

On the other hand, if the oil sump is under filled, at speed the sump level could be low at speed, from the oil in the top end not draining back fast enough to keep the oil sump pick up covered & it'll suck air & aerate the oil being pumped. The same sort of scenario could be happening if the top end has sludge, such that the top end oil returns are clogged up & the oil is draining back to the pan too slowly at speed to keep the oil sump topped up.

If the oil filter is defective, or has a volume flow/pressure drop problem across the filter media, you need to replace it without delay.
More thoughts for pondering. Let us know what you find.

 

Get an aftermarket oil pressure gauge. The factory gauges can't be trusted for an accurate reading. An electronic gauge would be good because it can be easier to T off the the existing oil pressure port on the engine and still keep the OE oil gauge working. The mechanical gauges are cheaper but not the greatest due to having to run a pressurized oil line into the cab to hook up to the gauge. Though I have had a mechanical oil pressure gauge on my 74' for going on 2 decades now without issue.

You should be running more than enough rpm to build over 50psi of oil pressure on the highway at those speeds. At idle and hot the oil pressure will obviously fall, most likely well under 40psi.

An Fl-1A filter is cheap and you should not need more than a quart of oil to fill back up with just changing the filter. I would change the filter and see if that does anything. There are some really crappy oil filters on the market.