Which weight oil to use?

[99TA]

In the owners manual for my 02 firebird with the 3800 engine it recommends using 5-30 to 60F and if its going to be warmer than 60F to use 10-30. Now someone PLEASE tell me what sense this makes because it makes no sense to me at all. Why not just use 5-30 all year round?

 

[StevieC]

Honda does funny things like this with it's lawn mowers... Not sure the reasoning... Maybe they want less flow when it's hotter?

I would follow the recommendations because the engineers know best IMO.

 

[FrankN4]

A 10w30 should/might have a higher HTHS and should/might have a heavier base with fewer VII thus would shear less, stand up to heat better.

There are of course exceptions. Some 5w30 oils have higher HTHS, higher 100C, and fewer VII than some other 10w30 oils.

 

[aquariuscsm]

I`d go with the thicker 10W30 out of the two.

 

[daman]

Makes no since un less your going to be running it HARD this summer maybe stick a 10w in there but i've had a few 3800's and all seen M1 5w30 all year around,even my '95 Bonneville SSEI super charged i ran 5w30(recomended 10w).

how hard do you plan on running it?

 

[Mr Nice]

I saw 10w30 SL rated lawn mowers oil for $5 at Home Depot the other day. I was using the old school 15w40 Delo in my mower without any problems.

 

[MGregoir]

The Buick V6 engine is 3/4 of a V8 with a split pin crank. Because of this and the odd loadings on the engine from the firing order, I think they required a heavier weight oil for mild climate conditions most of the time they were produced.

 

[joflewbyu2]

The 5w & 10W are the flow rates at a specific low temp. If your climate is cooler, go with the 5W for better cold starting flow and if it is warmer climate you should go with the 10W. The both 30 have the same hot temp flow.

 

[Mark888]

Generally speaking, a 10w30 oil is a bit thicker than a 5w30 oil of the same type, from the same manufacturer, even at high temps. It is myth that two different all x-30 oils have the same high temp operating characteristics.

 

[StevieC]

Originally Posted By: Mark888
Generally speaking, a 10w30 oil is a bit thicker than a 5w30 oil of the same type, from the same manufacturer, even at high temps. It is myth that two different all x-30 oils have the same high temp operating characteristics.


You opened a can of worms now...

 

[FrankN4]

Originally Posted By: Mark888
Generally speaking, a 10w30 oil is a bit thicker than a 5w30 oil of the same type, from the same manufacturer, even at high temps. It is myth that two different all x-30 oils have the same high temp operating characteristics.

The second number, in this case 30, indicates the grade of the oil. 30 grade goes from a 100C cSt of 9.3 to a 100C cSt of 12.49. You could also have a 30 grade with a HTHS of even 3.5, A3, or as low as 2.9(many are 3.0-3.1)

 

[ekpolk]

Originally Posted By: Mark888
Generally speaking, a 10w30 oil is a bit thicker than a 5w30 oil of the same type, from the same manufacturer, even at high temps. It is myth that two different all x-30 oils have the same high temp operating characteristics.


Who said that all 30 wts have "the same" high temp operating characteristics??? You're making a myth to attack. The properties of any oil are measurable in a lab (in an engine too, I suppose...). Looking at an oil's hot vis and HTHS vis will tell you most of what you want to know about its capabilities. It is a myth to generalize that 10w30s are, as a whole, "a bit thicker" than 5w30s from the same mfr. You've simple got to look at each maker's published numbers. Look at good old "German Castrol" -- a 0w30 oil. I don't know how many times I've heard someone claim it's "too thin" being a 0w-30, whereas in reality, at operating temps, it's substantially "thicker" than most 5w30s and 10w30s, at slightly over 12.1 cSt.

Do not generalize about "hot viscosity" or HTHS from the "w" grade of an oil. That's simply not a reliable way to judge motor oils.

 

[Trajan]

I used a 5w30 in my 1997 Camaro 3.8 for 3 of the 4yrs I had it. The last year I used 10w40. Didn't seem to hurt it any.

 

[J_Myler]

Were's Tall Paul when we're talking about 10W30?

 

[99TA]

I'm just giessing but i'll bet it has something to do with hot starts in warmer weather. In warmer weather they want the heavier oil on a hot start up to protect the crank. Otherwise it makes no sense, 30 wt is 30 wt.

 

[tig1]

M1 5-30EP year round with 10-12,000 OCIs.

 

[ATS-V]

The 3800 is an old design. The recommendation might be due to oils of the "day". My oil cap says 10w30, later years had 5w30 caps. IMO with synthetic oil it doesn't make a difference unless it's really cold (< 0F).

 

[FrankN4]

I'm just giessing but i'll bet it has something to do with hot starts in warmer weather. In warmer weather they want the heavier oil on a hot start up to protect the crank. Otherwise it makes no sense, 30 wt is 30 wt.

Quote:


The second number, in this case 30, indicates the grade of the oil. 30 grade goes from a 100C cSt of 9.3 to a 100C cSt of 12.49. You could also have a 30 grade with a HTHS of even 3.5, A3, or as low as 2.9(many are 3.0-3.1)


As far as I know, there is no such thing as a 30 weight oil, or any weight oil for that matter. Oil is sold in viscosity grades, not weights. A 30 grade can be just .01 cSt thicker than a 20 or just .01 cSt thinner than a 40. Two 30 grade oils, even from the same manufacturer, could be very different in base oil thickness, amount of VII, cold flow and high temp specks.

Mobil 1 makes a 5w30 with a 100C cSt of 11.3. Their 10w30 has a 100C cSt of only 10. Valvoline makes a 10w30 Synpower FS with a 100C cSt of 10.5 and a 3.0 HTHS. They make a 10w30 MaxLife FS with a 100C cSt of 11.7 and a HTHS of 3.5.

If you pick up an oil container and it says XW-30 on it, it means that it at least meets a given cold flow property and it is in a range of 9.3 cSt to 12.49 cSt(30 GRADE) at temperature(100C). You could put a 30 grade oil in your engine with a 100C cSt as low as 9.3 or as high as 12.5. You could put a 30 grade oil in your engine with a HTHS of only 2.9 or as high as 3.5.(maybe more or less, these are just on the market oils that I am aware of) One 0W-30/5w30/10W-30 is not necessarily the same as another, even if from the same manufacturer. You could get a 0w30 that had a higher HTHS and a higher 100C than another 10w30.

With the advent of GP II, II+, and III, without even considering GP IV, there is often little difference in base oils between the XW-30 oils. Lots of times we may think going to a 10w30 gives us a "thicker oil than a 0W or 5W. Than is no longer necessarily so. Sometimes the difference favors the 0W or 5W. Some will say a 10w30 will shear less than a 5w30. Of the same brand and type, there is some truth to this. However, there are 5w30 synthetics that will stay in grade longer(miles) than some other 10w30.

I am old enough to remember when you could go to a place called a "filling station" and buy something called "motor oil." It came in 25 cent, 30 cent and 35 cent with 35 cent being the best oil. It came in straight 20, 30, or 40. An oil change with an oil filter could cost you $5.00 if you let the filling station do it for you. Then you would fill up your tank and that could go as high as $2.00. Oil, Gasoline, Oil filters, and Prices have changed, a little, over the years.

 

[daman]

Originally Posted By: 97 GTP
The 3800 is an old design. The recommendation might be due to oils of the "day". My oil cap says 10w30, later years had 5w30 caps. IMO with synthetic oil it doesn't make a difference unless it's really cold (< 0F).

Al my 3800's('95,'95,'93)called for 5w30 except my SSEI SC called for 10w30..

 

[Jaymus]

My mamaw's 2000 Buick Park Avenue with the 3800 calls for 10w30 on the oil lid.