5w30 versus 10w30 oil

[MikeNW]

My owner's manual shows to use:
5w30 if the outside temp will be below 20F
10w30 if the outside temp will be above 20F

Hmmm. There is no upper limit for either oil. There is no lower limit shown for the 5w30.

Are there any drawbacks to using 5w30 all of the time? I mean, is it too thin for higher temps?
I use 10w30 Mobil 1 presently. This car has spent 98% of its life in SoCal or NW Arizona or Lower Alabama, hardly cold climates.
But will be in Ohio again, and it's colder there than Lower Alabama for sure.

[OldNuc]

Those guidelines are based on the average physical characteristics of dino oil available on the shelf when the first engine was designed, say 1987 or so. As you are using a synthetic or at least a synthetic blend with Mobil-1 I would not sweat it. The 10w-30 Mobil has a lower temperature cold pour point and lower cold cranking viscosity than any oil you could buy in 87 except a synthetic. You probably exceed the design specs for the engine oil greatly.

I would switch to the 5w-30 for winter in the frozen north though.

[eRic 02sc2]

Saturn retailer service departments fill S-series with 5w-30 all year...

[mr18436572]

In very cold climates, I would use 5w-30

I'm using 10w-30 in the SC2 here in AZ

[fdryer]

Originally Posted by MikeNW

... Are there any drawbacks to using 5w30 all of the time? I mean, is it too thin for higher temps?
I use 10w30 Mobil 1 presently. This car has spent 98% of its life in SoCal or NW Arizona or Lower Alabama, hardly cold climates.
But will be in Ohio again, and it's colder there than Lower Alabama for sure.

When asking if oil is too thin, you may be as confused as many about the oil ratings. Your answer lies in the second oil number after the 10Wnn or 5Wnn. The second number is the summer oil weight for conditions in hot temperatures. Below is the FSM chart. The summer weight (5W or 10W-30 meanas the anticipated outside temperatures where 30 weight oil wil work appropriately. As you can see, both 5W30 and 10W30 work above 100F temperatures. More than adequate for the Mid-States. The first oil number is of more concern as you move from sunny California to cold hard winters. Switching from 10W to 5W30 will allow better cold starting for engines and less strain on the battery/starter. You can always learn (the hard way) and use 10W30 in winter to find out how 10 weight oil will strain the battery and starter as temperatures drop. The oil thickening will make the starter turn slower and you'll know it and regret it. Simply using 5W30 oil will work all year round.

[mjoekingz28]

Some report lower consumption with 10w vs 5w.

I run 5w in the winter and 10w in the summer.

[OldNuc]

MikeNW;
Read the first several chapters of this document. It will answer your questions. http://www.bobistheoilguy.com/aehaas/

The FSM/Owners Manual recommendations are directed at he generic brain damaged owner who will unwittingly select the worst possible combination of oil and filter and fail to change either periodically.

It makes a huge difference in what the formulation and quality level of the oil is as to its applicability to the projected service conditions.

[SLCraig]

5 winter, 10 summer for me.

I've even run german castrol 0w30 in the winter, its thick at temp, but cranks great in the cold.

[OldNuc]

There are a couple of 0w-40 oils out there now, full synthetic though.

[1996SL11.9L]

in a warm climate with hi temps and a margional cooling system running the oil very hot, some of the multi-viscosity 30w oils will start to degrade back down towards their base stock (the 5w or 10w) and in hotter conditions the 10w will have more protection because it is heavier to start. Mind you the degrade is over time as the polymers that thicken with a rise in temp to thicken the oil to its warm weight (the 30) will sheer and break apart.

Some will say that the sheering effect actually makes the oil thicker but in the end that is why they recomended it for summer duty "back in the day" it can only degrade 20 numbers instead of 25 (more stable at temp over time)

As OldNuc says with the oils today its probable not very concerning. I run Penzoil Platnum 5w30 all year round

[The Critic]

Chances are, you and your engine will never notice the difference.

However, 10w-30 oils tend to have significantly lower volatility than 5w-30 oils. For instance, Valvoline Maxlife Synthetic 10w-30 has a NOACK volatility of 7%. The 5w-30 version is 9.5%.

[sdowney717]

Off hand I dont like any 20w engine oils
OEM made the switch to thin 20 wt oils to eke out a fractional fleet MPG increase at the expense of bearing wear. So if you like 1/3 mpg improvement go for it. Just dont think your bearings under pressure are going to like it. the oil film gets too thin and then you get metal contact. Why do you suppose cranks and bearing wear, it is fine 10 micron grit in the oil and or an oil film too thin to take the pressure. A good synthetic 5w-30 or 10w-30 with a purolater pure one is fine. Any 100% synthetic engine oil in the proper weight range is better than the best dino oil.

[John Olson]

Originally Posted by The Critic

Chances are, you and your engine will never notice the difference.

However, 10w-30 oils tend to have significantly lower volatility than 5w-30 oils. For instance, Valvoline Maxlife Synthetic 10w-30 has a NOACK volatility of 7%. The 5w-30 version is 9.5%.

I could not have said it better.

[manualman]

Please realize that the API viscosity rating tells you VERY little about the oil overall. You gotta do more homework. For example, Mobil 1 synthetic 10w30 will pump MUCH more easily than dino oil 5w30 when you try to start the car at 10 below zero F. HUH? Why? The specs only tell you the viscosity at 100C (212F) and 40C (IIRC). That simply doesn't say anything about the viscosity at 10 below. But synthetics have a MUCH higher viscosity index, which is a measure of how sensitive the viscosity is to temperature changes. If you can find an oil's "pour point" it is more useful in predicting if the car will start than the 5w vs 10w rating. Same goes for a published viscosity index....


I use Group III synthetic 10w30 (Walmart Supertech) in winter for the good cold pumping viscosity and dino 10w30 in the summer. I like 10w better simply because it has fewer of the exotic and fragile "viscosity index improver" compounds in it. Those chemicals help dino achieve the spread between the 5 and the 30 in 5w30 and 5w30 needs more than 10w30 (all else equal). Less is better in a Saturn because when oil gets trapped between our oil control rings and compression rings that stuff is the first thing to overheat and burn off into sludge. And you know what happens next: oil consumption!