Castrol Syntec 5W-50 vs others

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Sep 12, 2002
Why is 5W-50 at $4/qt while others are generally more than that? As you know i'm trying to find a suitable oil (and cost effective) for my 97k mile old 1981 Ford 302 V8. I think using a 30wt oil is too thin, as it seeps past the rings (my plugs were oil covered). Using 10W-40 seems to work, altho I can sometimes smell engine oil!! None of it seems to disappear tho. I was thinking about using 15W-50 or 20W-50 but it seems too thick for winter use. I primarily drive the 81 T-bird in winter weather (0F-30F). By too expensive, I mean anything above $4.50-$5/qt is too expensive.
I would never recommend a 5w50 oil, that spread is way too far. I think a 15w40 would be a better choice for your car over 5w50. But as I mentioned before, the 10w30 high mileage oils might work well too, since they are close to a 40wt.
I know that 5-50 is not that popular in this country but it worked fine for me in a 350 Chevy. Ran it for the last 135k and the engine now has 223k and still runs fine. No sludge visible in valve covers and no consumption yet. I have a uoa posted on this oil and numbers were not that bad considering it was run in the winter. Have always run extended drains on this oil. For the fun of it I am going to run Mobil 1 10-30 for a comparison to see if there is any improvement. Currenty running some 10-30 dino with "RX" before I switch over. The only difference I notice right now with the thinner oil is lower oil pressure at idle which is about 25psi compared to 35psi with the 5-50. At road speed there is no difference in pressure, 50psi with either weight. Also don't see much difference in fuel economy with either weight, averaging over 20mpg with either grade. While the 5-50 may cause problems in some engines I don't think it be any problem in a V8 like yours based on the results I have had. My 350 is a former police car with some hard usage likely in its first 87k of driving with changes longer then I would have done in that usage. Still after all this it runs like it has a lot of life still left. If the M1 does not show better results I may go back to 5-50 as I have in the past I found it priced as low as $2.50 a qt once in a while.
It's simply a matter of supply and demand ...the 5w-50 is less expensive since few people buy this grade. I'd run a 5w-40 or 10w-40 synthetic in this engine .... TS
A 5w-50 is a large spread and if bought as aCastrol Syntec too large. But better formulations with better base stock could handle large spreads. For example the 0w-40 MOBIL 1 is equally large for all intents and purposes and has gotten good results. The german castrol oils are pretty good, For example their 10w-60 is a strong oil and now has replaced the recommendation for 5w-30 in M3's. (Maybe in M5's too, but I better check on that) Fred... [Smile] [ March 29, 2003, 04:00 PM: Message edited by: palmerwmd ]
Metroplex, I have a 87 Crown Vic-302 with 221,000 mi. At 50k I started using Pensoil 5w50, around 150k changed to Castrol 5w50 because of availabilty. Around 200k changed to Castrol dino 5w30. 2yrs later at 221k, motor runs and pulls great. I changed oil every 3000-3500 with both the synthetic and dino. Motor uses about 1/2 3000k. Last month, the intake gasket was leaking about a gal. of anti-freeze every other day, so after much soul-searching I decided to have my dealership replace the intake gasket. When I stopped by to checked on the car, the mechanic 'demanded' to know what kind of oil I used. He said it was one of the cleanest engines that he had every seen and showed me where you usually see sludge desposits and my motor had none. I was very happy using the 5w50 syn oils. When I started using them, I noticed that the 'ticking' noise at start-up was almost eliminated and I got 5% more gas mileage.
You can safely use the Syntec 5-50. I'm running it now and the car runs better than ever...better than M-1 15-50...
Originally posted by Dr. T: You can safely use the Syntec 5-50. I'm running it now and the car runs better than ever...better than M-1 15-50...
Do you plan on doing a UOA on it?
Haven't thought of it. The last time I did a UOA was when I suspected the dealer using the conventional BMW 15-40 when I asked them to use the 5-40 synthetic as the cheaper 15-40 was listed on my invoice right under "customer wants synthetic". The mechanic said he still had the empty box of synthetic 5-40 in front of him so this is what he used, so I go a price break...but, I didn't believe them. So I did the UOA to determine the grade. Will I do one now? Maybe...I'll need to do another round though in order to get rid of the sludge build up....
I think most people on this message board dislike the 5W-50 grade. We have two UOA's of Castrol Syntec 5W-50 that to my untrained eye look very good. One of those UOA's was on a Ford van with a 4.2L V6 that now would use 5W-20 motor oil if it was installed in a 2001 or newer Ford and it still did well. I have seen one UOA of Castrol Syntec 10W-30 that Patman posted and it looked mediocre. At least the 5W-50 grade seems to hold up well. Is the real reson why so maney people hate Castrol Syntec just because Castrol uses a group III oil and not a PAO? There is no doubt that all else being equal a PAO formulated synthetic oil will be better than a group IV synthetic but it still seems to me that what really counts is the oils performance and not how it's made. I hope I am not beating a dead horse here but who here has really had poor results with Castrol Syntec?
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