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Viscosity debate....

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39K views 96 replies 40 participants last post by  MitchW  
#1 ·
So I have heard that running 5W/50 in the summer is good for spiders. I have also heard 10W/40, and 10W/30.

I would like to ask what oils you all use, brand and viscosity, so i can get a better idea.

Cheers.
 
#3 ·
I have used Castrol GTX 20W50 since 1988. Neither my '74 2000GTV or my '81 Spider have "complained". I have heard the debates about vegetable oils and synthetics and additives and PTFE ad-nauseum, but I am of the school of: "Don't fix what ain't broke". One thing I must point out though is that we don't get any snow or sub-zero temperatures here (we range between 5 - 35 degrees C), I don't know if this may change things.
 
#5 ·
While I've used GTX 20w-50 in the past, it is highly unlikely I will be using it any more. The zinc level in GTX, as in most other :rolleyes:"modern" oils, has taken a severe hit. Diesel oils (Delo 400, Rotella) are 15w-40 and, while they are at zinc levels were in regular dino oil, are also going to suffer with the low sulfur emission oils. I've been threatening to take a look at Valvoline Motorcycle (dino) 4 stroke 20w-50. Right now I have the Delo in it. To :(get rid of my last supply of GTX 20w-50, I'll probably put 6 qts in along with 2-15 oz bottles of red STP.
 

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#47 · (Edited)
racing oil vs. Castrol GTX 20w-50



I have an 87 Spider Veloce and have always done my own oil changes on the family cars. Recently two mechanics (including one with 25 years experience with Alfas and BMWs) suggested using Valvoline 20w-50 racing oil because of the high ZDDP levels that prevent premature camshaft wear. I live in a moderate climate in NC, don't do much "racing" and worry about the Valvoline not having the everyday qualities that a normal driver needs. Meanwhile, I have 28 quarts of GTX 20w-50 sitting on the shelf. Any ideas on one oil vs. the other?
 
#8 ·
GTX 20w-50 is good for the summer, but I use 5 - 50 year round because I use my spider well into December (in NJ) I also recently changed the gearbox from spirax to a 75-90 syntetic for the same reason, easier to shift in the winter.
On a previous spider I ised castrol 10-40 year round from 1986 to 1993, I do not recomment 10-40 because I had to have the engine rebuilt at 80K miles.
this is my personal experience, I used to alternate 20-50 in summer and 5-50 in winter but I don't see the point in doing this anymore. I drive the car 6k miler per year and usually a single oil change in the summer with 5-50 is good for the whole year. I have been using Purolator filters.
 
#9 · (Edited)
On a previous spider I used castrol 10-40 year round from 1986 to 1993, I do not recommend 10-40 because I had to have the engine rebuilt at 80K miles.
10w-40 (dino anyway) is not a good oil to use according to what has been written nowadays. The spread between #'s indicates too many Vicosity Index Improvers have been added which is not a good thing. :(I've used it for many years until I heard of this. I now use 15w-40 Delo in my Chevy V-8's in those instances when I used the 10w-40. Even though it doesn't seem like a big difference (40-10=30 vs. 40-15=25), apparently it is. I also use the 15w-40 in my last (Dec.) Alfa fill of the year and leave it in until the real hot weather (July).
 
#10 ·
+1 for what lowmileage said. You want to avoid too much of a spread, so I'd stay away from 5W-50 for sure. I've used the Rotella 15W-40 and Mobil 1 15w-50, which has better ZDDP levels than some of their other blends although people still debate whether it's "good enough" for older engines.

Interestingly, I read someone comparing the "spread" in various oils by dividing (50/5-10, 40/15=2.67, 50/15=3.33). Regardless, the less the spread the better. My only other experience is that with very low "cold" numbers (0W-40, 5W-50) I've gotten some nervously-loud valve train noise on older cars until they warm up. So I don't go any lower than I need to for expected temperatures.
 
#11 · (Edited)
You want to avoid too much of a spread, so I'd stay away from 5W-50 for sure.
I'm not certain but the "spread of the numbers theory" might be different (may not apply as in the case for dino oils) for syn oils. I know it is for M1 5w-30 which in a dino contains more than the ideal mix of VII's but is good in the M1 instance.

why is 10w-40 bad? - Ford Truck Enthusiasts Forums

Oil. - Dodge Caliber Forums see post #4

ps. 20w-50 in a dino is OK . Theory blown in that instance too.
 
#13 ·
I'm another user of Mobil 1 15w/50 in all my Alfa's. Some of the newest cars (i.e a friend's '06 BMW) use something much thinner, like a 0w/40, but Mobil 1 15w/50 is probably the closest to matching the original Alfa spec back in the day. I might try something else in winter, if I lived in a colder climate, but 40F is about as cold as it really gets around here.
 
#14 ·
just to be clear. these guys are not talking about the Mobil1 15w50 EXTENDED, which is the usual one you find. theyre talking about the dark-red-labeled plain 15w50. the only place ive found it consistently is at Wal-Mart, in the large 5quart bottles.
 
#17 · (Edited)
I think the extended has more detergents for one thing
"Mobil 1 Extended Performance oils are uniquely designed to provide outstanding levels of performance, cleaning power and engine protection, even during longer oil change intervals."

Mobil 1 Extended Performance

But I doubt us Alfa owners would leave it in for such an extended period plus I'd be afraid with all the detergents it might loosen stuff up and/or clean up too much around the gaskets.

The regular may have more zinc:

"Mobil 1 15W-50 is also recommended for older valve train designs that may benefit from a higher level of anti-wear normally not required for newer generation vehicles"

Mobil 1 15W-50

Higher Visocity Index and Flash point also in the regular.
 

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#18 ·
I guess Alfa may have been at the race track or something that day and missed the class on maximum viscosity spread. The Alfa recommended oil from 1990 and up is 10w-40. 1974-1989 was 10w-50.

Guess someone ought to tell Alfa they've got it all wrong, eh? :rolleyes:
 
#20 ·
#26 ·
I don't think brand names have that much to do about it. Thier all about the same when you read the label, they all conform to the same standards. My dad used to say you should stick to one brand, in other words if you start using Valvoline, you shouldn't add Pnsoil later because sometimes different sources of crud don't mix well. My hot-rod mechanic says if the owners manual says 10W40, to use 10W30. May using the 15W50 on the my S4 is not what I should be using. I'm using 10W30 on my 400hp Ford hot rod and a can or BG-MOA
 
#30 · (Edited)
Picking for no other reason than my own amusement at a couple spots in the above linked article:

A thinner oil can more easily and quickly be 'pumped-up' to the critical parts of the engine, takes less energy to move it around, helps the engine to produce more power
Did I not just say that? hehe

Unless your car is an actual bonafide 'RACE CAR'- no city driving, no idling, no stop and go traffic, no foul weather driving, etc...- Do NOT use 'racing' oil in your engine. Racing oil has a very narrow and specific additive package designs for engines that are used in racing situations, like constant high rpm operation, steady speeds, no stop and go, no foul weather, etc...
Spoken like a man who has truly never been in or seen an endurance road course race. (strange what some people define as racing that others do not even acknowledge exists. It ain't all about running around in circles)

As an example: start with 10W-30, and at 500 miles top it off. If 1,000 miles later you are a quart or half a quart low, record it and continue with the test. At 3,000 miles, if you have had to add more than a quart counting from the first 500 mile top-off, then you should use 10W-40 on the succeeding oil change.

Record your results again. If the 10W-40 does not volatize as readily then you should stick with that. However, if it still burns away, then try 20W-50.
Must not be talking about an Alfa engine :D



As I said, for my own amusement, becuase I am indeed easily amused. Nothing more, nothing less.
 
#31 ·
I think the oil that is best for the bottom might not be the best for the top?
my 3l V6 liked the 0-40 moble1 the best. but after I redid it the top would knock with the S cams (the oil jets might have somthing to do with it too) so I went to the 15W50 moble 1 and it seems to like that a lot.

I am runing the 15-40 sync shell truck oil but it seem to not like that so much as it started to burn oil so I will be going back to the moble 15w50.

but the way I see it is, if you have a working gage(rare in a alfa) you should run as thin as you can and keep the oil PSI. if you go to thick the flow will be down and all the oil will be going in to the bypass valve. runing 20W50 dino I runed the bottom of my old v6 it was still runing but knocking at idle. On tear down the the shells where wiped out. this is what happens with too thick and cold runing. it is the same as runing with no oil.

you want flow in the bearings not the bypass. but you also need it keep up the PSI when HOT.
the syn seems to work welll with this. but the dyno would peg at cold and run low hot.

I drive my car every day to work and I put on the miles. so I need it to work and run when cold or when hot.


that is my $0.02