Which Weight do you run?

So I'm just curious, what is your opinion on what to run? its 35 degrees and lower here in Pittsburgh, and its about time for me to change my oil. I'm running Castrol GTX 10w-40 at the moment, and I always have. But I also Never drove as much as I do now (30-45 minutes a day to college). Should I drop it down to 10w-30 for easier start up? Would it cause more harm than good? Like I said, I've never put anything other than 10w-40 Castrol in it. Its a 75' Mav with a 250I6 w/ 39,000 miles on it

 

yep.. thinner oil reduces start up wear in cold weather. Which is where the bulk of engine wear occurs in all but full on racing engines. Thinner oil never hurts mileage either.

 

10W is the COLD weight, if you want easier cold starting go to a 5W or even 0W... IE 5W-30 or something like Mobil 1 0W-40 if you want something exotic(used it in my supercharged Marauder)

Cold 10W-30 is similar to 10W-40, it's only thinner when hot...

 

So running highway (65-75mph)wouldn't create too much heat to the point the oil would become too thin?

 

while that's certainly true to some degree.. consider that 30 weight oil also flows better in cold weather than 40 weight at startup. It's easy to tell the difference between the two when you've poured both weights out of the bottle coming off a cold garage shelf.

And cold 10/50 is like honey compared to 10/30 in the same environment regardless of that 10 weight similarity.

 

If your engine has normal bearing clearances, doesn't have high valve spring pressures and maintains 10Lb oil pressure for each 1000 RPM, a 0/5W-30 will be fine...

 

true that. I'd probably run a 5 weight in anything colder than 30 deegrees or so.

If I were to switch to a 0 weight.. the motor would have to be fresher and running positive valve stem seals though. And even then.. it would have to be synthetic to reduce burn off due to less than perfect machining tolerances these motors are known for..

Could even get by with much less than 10lbs per 1,000rpm on that little motor too.

 

Okay, so 5w-40 would protect as well as 10w-40 at normal operating temperatures?

 

That mostly depends on the oil's viscosity index but that's getting a little deep for this discussion... I'll agree that at 32*F a 10W-30 will likely be a little thinner than a 10W-40 but depending on the VI, a quality synthetic 10W-40 will be thinner at -10F than a run of the mill dino 10W-30...

 

To the OP, remember this... ALL oil without exception is really too thick at startup(even so a 0W-20 at 100*F), so for cold starting a high quality 5W-30, is going to your best bet in the winter...

While Castrol GTX is a good oil there are others that are better, especially in cold weather...

 

for that motor yes.. any premium oil will do the job just fine. Then switch back to your regular poison in the springtime.

yep. Also good to keep in mind that shear strength of an oil doesn't always go up with higher VI's. That's where the hi-tech additive packages come into play.

And as usual.. always a pleasure comparing notes with you, Comet.

 

your car should be 10w30 from get go
you can go to 5w30 for easier start up or even 0w30 if its offered(never really looked into it)

The most engine wear comes from initial start up

one big thing about todays oils from your local gas,station,auto parts store and wal-mart is its the wrong oil formulation for our cars.
Todays oils have heavy Calcium concentration detergents which strips any metal to metal barriers(for emissions) and you get metal to metal contact..which either results in a catastrofic failure in your valvetrain or excessive wear(mainly flat cam lobes and lifter wear)

Our engines need Zinc and phospurous (ZDDP)
simply adding a bottle to any oil isnt the best solution as ZDDP adds a layer of protection while calcium strips it(counteracts each other)

Best to go with oil that has the correct ZDDP levels which would be
Joe Gibbs HR-2(dino) and HR-4(synthetic) or AMSoil Z-Rod(synthetic)

EDIT
gonna Hijack slightly.
Do you ever hit up any car shows in the 412 or 724 area code?

 

Unless you're running high high lift cam with high valve spring pressures things aren't as bad as being made out... If this metal to metal contact was as you say how are new engines running 300K mi on today's oils???

Yes zinc has been reduced but I don't know of any oil that doesn't have around 700 PPM, which is plenty for stock engines especially if already broken in...

The Mobil 1 0W-40 I mentioned still has 1100 PPM which is within 150 PPM of what oils had before the reduction(see link)... It wasn't mandated that 40W oils reduce zinc though most have done so...

http://www.mobiloil.com/USA-English/MotorOil/Files/Mobil_1_Product_Guide.pdf

This no zinc, the sky is falling routine is mostly an agenda to push boutique oils that have a $$$ price tag...

 

Any oil is better than no oil...

10-w30 summer, 5-w30 winter. All my new vehicles recommend it, so why not my older vehicle?

 

We've had this discussion before.

http://www.bobistheoilguy.com/motor-oil-101/

"The greatest confusion is because of the way motor oils are labeled. It is an old system and is confusing to many people. I know the person is confused when they say that a 0W-30 oil is too thin for their engine because the old manual says to use 10W-30. This is wrong."


"...average oil temperature is 212°F, the boiling point of water. On the track that temperature is up to 302°F. It is important to realize that these are two different operating environments and require different oils."

" 0W-30 grade oil is not thinner than a 10W-30 oil. They both have the same thickness at operating temperature. The 0W-30 simply does not get as thick on cooling as the 10W-30. Both are still way to thick to lubricate an engine at startup."
"...straight 30 grade oil has a thickness of 10 at the normal operating temperature of your engine. The multi-grade oils 0W-30 and 10W-30 also have a thickness of 10 at 212°F."