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Mobil 1 15W50 Too Thick For Summer?

xccter

Active member
Joined
Jul 9, 2006
Messages
30
Location
Frederick and Kent Island, MD
Corvette
71 Ontario Orange 4spd Coupe/88 Dark Red Z52 Coupe
'71 350/270 4spd, a/c, power s/b/w, bone stock, 88k miles.

I have 5 qts of Mobil 1 15W50 left over from the 454cid Mercruiser I had in my SeaRay (Sport Cruiser Yacht).

Question: Is this too thick for summer use in my '71? The thickest multi viscosity oil recommended in the GM SM is 20W40 for temperatures above 20 degrees before the next oil change.

I'm sure that in '71 there was no such thing as a 15W50 grade oil, much less a full synthetic.

I wouldn't even consider using it during cold weather months, but it's summer and I don't want to throw $26 of Mobil 1 out at the recycle place.

Opinions or advise please.
 

Wayne robson

Well-known member
Joined
Feb 24, 2007
Messages
169
Location
australia
Corvette
sold my last corvette.
I would think first.

Hello Xccter, i would like to tell you some of my 62 years experiances and dozens of makes of cars ive owned with oils. in the last 20 to 30 years ive used Penzzoil and castrol regular oil in all my old cars, 3 porsches 911, 4 alfas romeos, 2 jaguars xke, and xk120, 1 mercedes 450 SL ,2 Cadilacs, 9 buicks, 1 corvette. I do what the original handbook says use the oppropriate oil weight for the temperatures example 10=30 in winter,and change every year yo 10+40 for summer, all of those cars and others i have not mentioned because they are australian holdens and falcons.etc, i have never had to pull a motor or remove a head because of wear. My first car a 39 buick straight eight i used Houghtons motor oil it was immported from US 100% pennsylvania crude. With the modern engines today with higher revs, modern Alloys , and finer tollerences, turbos, superchargers, ok a modern Synthetic is fine, All the modern cars ive owned ive used the same except for a later Porsche 911 which inccidently reccomends mobil 1 synthetic. Back in 1976 until 1988 i managed a General motors Holden francise in New zealand, Holden is a car made there and Australia, we used to sell and service the holden monaro and statesman, , 253 v8, and 308 v8, Mobil oil introduced the synthetic oil i think it was 1985 or 86, hard to remember, we started useing it and after some few months customers started coming in with noisy engines suspect bearings, and oil consumption, we had to pull alot of engines,re hone cylinder bores, and replace bearings because of this, under warrantee of coarse, so we contacted mobil oil they reccomended that we go back to regular mobil oil which we always used anyway, within a few months the dealership was sold to a toyota franchise and i never found out what happened about the synthetic problem, because of that problem i would never use synthetic oil in any of my older classics. And remember when oil gets darker and dirty you know its doing its job. Also one of the best products in the bussiness Honda, reccomends, Feo, high performance engine oil 10+w30 for all Honda products its sold world wide, for all seasons non synthetic. ive used that in 3 late model hondas ive owned, regards wayne.
 

xccter

Active member
Joined
Jul 9, 2006
Messages
30
Location
Frederick and Kent Island, MD
Corvette
71 Ontario Orange 4spd Coupe/88 Dark Red Z52 Coupe
Wayne,

Thanks for sharing your considerable experiences. I've been using Mobil1 in all my vehicles since about 1988. I even use it in my lawn tractor and other yard equipment since I always have plenty of it around. I used it in a '65 Mustang show car for all those years, and never had a problem with it or in any of my Corvettes or family vehicles.

Put aside the synthetic thing for the time being, and just consider the viscosity issue.

With daily temps near the Washington, DC area in the 80-90s all summer, do you think I can use this 15W50 grade oil without a flow issue at start-up?

I'll use it for the summer and go back to my usual 10W30 when autumn gets here.

Thanks for your input.

:v
 

Bobsvette

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Joined
May 14, 2006
Messages
204
Location
Enfield, ct
Corvette
2019 Torch Red Grand Sport
I don't know. I never used oil that thick in anything except a american rambler that was a winter beater that the cam bushings were so worn and you could hear the piston's slapping 26.00 will that break ya? throw that molasses on e-bay and get the proper fluid a corvette deserves! :bash
 

Wayne robson

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Joined
Feb 24, 2007
Messages
169
Location
australia
Corvette
sold my last corvette.
following on

Hello Xccter yes 15w is fine for those temperatures , see the first figure is the start up oil weight, the second figure is the weight when it is up to normal working temps..One of the only makes of cars that recommends, 15 = 50 w in regular oil, is Alfa Romeo in there 1700 and 2000cc twin overhead cam, engines, with spica fuel injection. in 1967 to 1975. regards wayne.
 

xccter

Active member
Joined
Jul 9, 2006
Messages
30
Location
Frederick and Kent Island, MD
Corvette
71 Ontario Orange 4spd Coupe/88 Dark Red Z52 Coupe
Follow-Up

I changed the oil and filter this afternoon from Mobil 1 5W30 to the Mobil 1 15W50. Drove 96 miles to my second home on the Chesapeake like I do most weekends, and this is what I noticed.

Outside air temperature near 80. The oil pressure at cruise (70mph/2800rpm) was just shy of the 35psi mark. Just a little higher than what it was with the 5W30 at the same speed.

At idle (850+/-), after driving 96 miles at hiway speeds, the oil pressure was just short of the 1/2 way mark between 0 and 35 (15psi?).

That was a noticeable improvement over the "barely above zero" reading I was getting with the 5W30 at idle when hot.

There you have it.

:)
 

jims427400

Well-known member
Joined
Jun 7, 2005
Messages
763
Location
Temperance Michigan
Corvette
67 427 tripower,68 427 tripower,04 Z16, 62 340hp
No comment on the oil BUT those C2 side pipes look awsome on your C3. I cant say I've ever seen that before..
 

xccter

Active member
Joined
Jul 9, 2006
Messages
30
Location
Frederick and Kent Island, MD
Corvette
71 Ontario Orange 4spd Coupe/88 Dark Red Z52 Coupe
No comment on the oil BUT those C2 side pipes look awsome on your C3. I cant say I've ever seen that before..

Thanks. I almost always get the same favorable comments everywhere I go from people that know what they're looking at.

Sometimes it bugs me, as I have tried to stay as close to stock in so many other areas, but...
 

xccter

Active member
Joined
Jul 9, 2006
Messages
30
Location
Frederick and Kent Island, MD
Corvette
71 Ontario Orange 4spd Coupe/88 Dark Red Z52 Coupe
For the summer months anyway. Only has 88k miles on it, so I'll be going back to 10W30 when the weather cools in the fall. I generally drive the '71 at least one day per month in the winter when the roads are clear and the sun is shining. I don't think I could go more than a month without driving it.

:)
 

xccter

Active member
Joined
Jul 9, 2006
Messages
30
Location
Frederick and Kent Island, MD
Corvette
71 Ontario Orange 4spd Coupe/88 Dark Red Z52 Coupe
xccter, might you have a problem with your oil pump?

I've been wrong before, but it's been my experience that oil pumps either work or fail completely, like a pump drive shaft breaking. Talking to folks here and elsewhere leads me to believe the pump is fine, as mine and other's gauges are reading about the same.

I see the signs for Millersville every time I drive back and forth from Frederick and Kent Island. Enjoy this great weather we're having.

:D
 

pws69

Well-known member
Joined
Dec 11, 2002
Messages
94
Location
Massachusetts
'71 350/270 4spd, a/c, power s/b/w, bone stock, 88k miles.

I have 5 qts of Mobil 1 15W50 left over from the 454cid Mercruiser I had in my SeaRay (Sport Cruiser Yacht).

Question: Is this too thick for summer use in my '71? The thickest multi viscosity oil recommended in the GM SM is 20W40 for temperatures above 20 degrees before the next oil change.

I'm sure that in '71 there was no such thing as a 15W50 grade oil, much less a full synthetic.

I wouldn't even consider using it during cold weather months, but it's summer and I don't want to throw $26 of Mobil 1 out at the recycle place.

Opinions or advise please.

That's all I have used in my 350/350 since breakin after the rebuild several years ago. It likes it a lot!!
 

Vette79

Well-known member
Joined
Jan 23, 2007
Messages
1,392
Location
Millersville, MD
Corvette
1979 L-48 Black Coupe
xccter, yea Frederick is not far away. The weather is definately getting better out here. By the way, I thought otherwise about an oil pump. Maybe someone could chime in to confirm or not!
 

windrider50

Well-known member
Joined
Oct 1, 2002
Messages
51
Location
NJ
Corvette
1996 CE LT-4 6 spd; 1972 BB, T Top "Boomer"
On a relatively fresh bottom end, with 15w-40 Mobil1 in my 72 454, and the water temp about 190, at idle (800 rpm), my oil press is about 40 lbs/in*2, and at cruise (2700 rpm), it reads around 65 lbs / in*2.

YRMV.

Cheers

:beer

BB NJ Ken
 

USNA1969

Well-known member
Joined
Sep 12, 2005
Messages
93
Location
Maryland
Corvette
1972 Big Block/4-Speed
I can't find the post now, but someone on this forum recommended Shell Rotella oil for older engines because it contains zinc. My recollection is that they recommended 10W40. Maybe someone else remembers that post and can clarify.
 
Joined
Jan 1, 2002
Messages
7,246
Location
Washington, Michigan
Corvette
'67 Marina Blue Convertible
Rotella and the other CI-4 and CJ-4 diesel oils (Mobil Delvac, Chevron Delo, etc.) have plenty of ZDDP, and are most commonly found in 15W40 weight, although others (like 10W30) are also available. You'll find it at Costco, Sam's, Wal-Mart, etc., or at any truck stop.

:beer
 

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