20W50 oil recommendations ?s

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Aug 20, 2002
I would like to ask if anyone {off the top of their head} would know which of common 20W50 oils have the highest viscosities at normal running temps. The reason I ask such a "off the wall" question is because I just bought a '90 Mustang GT with 177K miles. The oil pressure is a bit too low and I figure a heavier weight oil might bring up the pressure. I know it's a band aid at best, I would just like to put off a motor swap for as long as I can. Thing runs great except for the oil pressure. It also uses {and leaks} a bit of oil. Bout a quart or two in 3K miles depending on how it's driven, so I would like to run a dino oil for economy. I would change it in the 3-4K range. How bout it? I'm thinking Castrol. Any help would be greatly appreciated.
First I do not know the answere off the top of my head I will need to do some research.Second I do not think it is going to matter much. The type of oil pressure increase you are going to get will not do anything for you. You are simply putting in an oil that has more resistance to flow.So while you will see an increase in pressure you also get a drop in flow. So while it might cushion the parts better it is not going to drasticly make up for worn main bearing, worn oil pump and leaking seals. If you can get the leaking under control you would be much better off with a high quality synthetic like 10W40 Redline or Amsoil for preventing wear, reduceing friction and protecting under high shear conditions. Auto-RX comes highly recommended for stoping leaks and cleaning out all the built up sludge in an engine. I ordered their special the other night. You might want to look into it. Goodluck!!!
Thanks for the advice. I really don't want to put much work into the motor. I figure that with 177K and somewhat low oil pressure, I will be replacing it in a year or so anyway. Was just wanting to bring the pressure up 10 psi or so. Basically just so I don't have to look at a low guage. Once had a 68 Ply. Valient that had over 300K mile on the original motor. The idiot light started coming on at idle. Changed to 20W50 and it went away-for about a year. When it came back, I still drove it for nearly a year with no oil pressure at idle. It finally gave up the ghost once it stayed on all the time-lasted about two months like that. Yep,,,,it finally spun a main bearing. Slant sixes are good motors! Poor thing had maybe 10-20 oil changes in about 20 years {my dad wasn't very mechanical nor did he care much for things mechanical! Just putting off the motor swap as long as I can. Once again thanks for your recommendations. Anyone else. Castrol or Valvaline? Maybe 15W50 Mystic?
I have had excellent results with many vehcles with the increase to 20w50 (or one grade from where you are) for people with consumption. Can buy you time with this. But you may be a canidate for AutoRX to get rid of what sludge might be blocking your pump intake and cleaning the seals and rings. [ May 04, 2003, 08:21 AM: Message edited by: widman ]
how about some kind of mixed fleet {gasoline or diesel} 15-40? it should flow a little better than the 20-50, and the detergent package being more robust, would help clean out the motor as well. i see where the delo or rotellas are well thought of. i wouldn't use a synthetic in the engine considering it's already using quite a bit of oil and has low oil pressure. run the 15-40 till it drops, then when you put the new or rebuilt motor in it, go to the high quality synthetics...penz
Judd, just from personal experience, I've always found Castrol oils eg. GTX to be on the thicker side compared to Valvoline for eg.. No experiece with Penzoil. Q.S. 20-50 may rank up there with Castrol's as well.
It's "baker's dozen" years old and has 177K on it! **** good service IMHO for a 302 that was probably never "babied" a day in its life! The HD 15W-40 & Auto-Rx comments sure make sense to me, especially if you think that the previous owner(s?) may have run her hard & put her away wet! [Burnout] Cleaning up the inside might just give you the additional oil pressure you are looking for. Maybe eventually going to the Amsoil ARO 20W-50 100% synthetic if you really felt like it. How's the compression? Getting a couple more years just gives you more time to plan what you put in better. [Cheers!]
Thanks for all the help fellers. I think I will do the 15W50 Mystic {diesel oil} to clean up the motor for a few changes then go back to GTX. I really like the idea of the Auto-RX but I really don't want to do any ordering. Would it really be worth my while? Would ya'll do it if you were me? BTW, the original owner changed the oil at 5K intervals with pretty much any dino oil-whatever the "Jippy" Lube had.
Oil isn't a cleaner, Auto-rx is. As always use the right tool for the job. Auto-Rx for your case is a no-brainer IMO. Ordering is very simple, and I received mine in 5 days on the other side of the world. How can you go wrong?
I have three engines that have been on this Castrol GTX 20w-50 for many miles with no problems. My boat has 3000 hours using this oil in a diesel 4 cyl. My toyota Cressida has 100,000+ on this oil weight and 250,000 total on Castrol GTX. My Triumph TR3 has 125,000 using this oil almost the entire time.
Originally posted by Judd: The reason I ask such a "off the wall" question is because I just bought a '90 Mustang GT with 177K miles. The oil pressure is a bit too low and I figure a heavier weight oil might bring up the pressure.
how are you determining the oil pressure? those engines do not have oiling or bearing problems. typical failure modes are skipped timing chain, detonation damage... oh, wait, i take that back. a worn thrust bearing is a common problem, but this rarely results in lower oil pressure (in these engines). the stock pressure gauge cannot be trusted at all. -michael
Yep, the ford gauge is only an idiot light. It does not show the pressure at all. It only shows that you do have presure. richard
Both you guys might be right-on with the oil sender idea. It may well have a problem. I compared it to other Mustangs I've had and a friends 90 model LX. Basically the "shown" oil pressure is about half of the other gauges I've seen. On a hot idle, the needle sits just above the very first line. It goes up a smidge when the rpm goes up but even then it's still at the very bottom of the "normal" range. I will throw a mechanical gauge on it to double check. I just figure that with 177K and my experience with several other 302s, the oil pressure was low. Would be best to double check, Thanks for all the relies. [Smile]
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