Blending motor oils to raise or lower viscosity

David Neibert

David Neibert

SCCoA Admin
I'm getting ready to change oil on the turbo car and I can't find the oil weight I'm looking for in Valvoline full synthetic. For summer I would normally use something on the thick side like 20/50 and for winter 10/40. I noticed that even in summer when using the 20/50 the motor rattles a little at initial start but quiets down as soon as motor gets up to about 150 degrees. I used to run the 20/50 all year round but I was afraid I was going to break the oil pump drive shaft if I goosed the motor when it was cold. Last time I changed it was during the winter and I think I used 15/40 and the motor sounded much quieter at initial start even when cold, same is true in summer weather like we have now.

I'm assuming this is because the 20/50 oil is too thick (like honey) until it heats up, so I've decided to go with a lighter oil all year round. I also recall that Dave Dalke found that my wrist pin bushings were in pretty bad shape when he tore down my old 3.8 motor that was running 20/50 all year round, and he thought it may be because of poor oiling. Problem is I couldn't find the Valvoline synthetic race oil I've been using in anything but 10/30 and 20/50. It takes 7 quarts for this motor so I was thinking I could just use 3 qts of 10/30 and 4 qts of 20/50 and end up with an average viscosity of 15.7/41.4.

Are my assumptions on lowering the viscosity by blending and averaging the two weights correct ?

David
 
Ever think of running a 10w60 full synthetic like what bmw puts in the m cars????

Seems like a good oil for your pourpose. Its made by castrol though.
 
Why do you use such a heavy weight oil on a high hp motor? I was always under the impression only use of 20/50 or similar on old worn tired high mileage motors, not race ready fresh high hp motor. Obviously you know better then I.
as for mixing I don't see why not as long as your running the same brand, I'd assume they would mix to your preferred viscosity.
 
David Neibert said:
I'm getting ready to change oil on the turbo car and I can't find the oil weight I'm looking for in Valvoline full synthetic. For summer I would normally use something on the thick side like 20/50 and for winter 10/40. I noticed that even in summer when using the 20/50 the motor rattles a little at initial start but quiets down as soon as motor gets up to about 150 degrees. I used to run the 20/50 all year round but I was afraid I was going to break the oil pump drive shaft if I goosed the motor when it was cold. Last time I changed it was during the winter and I think I used 15/40 and the motor sounded much quieter at initial start even when cold, same is true in summer weather like we have now.

I'm assuming this is because the 20/50 oil is too thick (like honey) until it heats up, so I've decided to go with a lighter oil all year round. I also recall that Dave Dalke found that my wrist pin bushings were in pretty bad shape when he tore down my old 3.8 motor that was running 20/50 all year round, and he thought it may be because of poor oiling. Problem is I couldn't find the Valvoline synthetic race oil I've been using in anything but 10/30 and 20/50. It takes 7 quarts for this motor so I was thinking I could just use 3 qts of 10/30 and 4 qts of 20/50 and end up with an average viscosity of 15.7/41.4.

Are my assumptions on lowering the viscosity by blending and averaging the two weights correct ?

David
Click to expand...

What kind of rattle is it? Valves, lifters etc.?
Since the late 80's most engines need no more than a 10W-30 oil due to tight tolerances in the engine. Thicker oil can actually cause other problems when trying to solve a problem.

My suggestion is try the AMSOIL RD30 (10W-30) racing oil. It is very high in zinc and phos for better wear protection and will flow faster on start up than a 20W-50 will.

If you prefer a 10W-40 then try AMSOIL AMO 10W-40 this oil is high in zinc and phos too. These two oils are man made 100% Synthetic oil not a hydrocracked refined petroluem oil that the S.A.E. mandated that can be sold as a synthetic oil when Mobil sued Castrol back in the late 1990's.

If you do not have a source to buy AMSOIL you may go to my website and click on the AMSOIL online store.

www.GetTheBestOil.com
 
rzibilske77 said:
Why do you use such a heavy weight oil on a high hp motor? I was always under the impression only use of 20/50 or similar on old worn tired high mileage motors, not race ready fresh high hp motor. Obviously you know better then I.
as for mixing I don't see why not as long as your running the same brand, I'd assume they would mix to your preferred viscosity.
Click to expand...

The heavier weight oil holds up better to the high oil temps. The oil gets very hot in this motor because it also lubricates and to some extent cools the turbo. That also why I use this $8.50 a quart full synthetic stuff and change it every 1000-1500 miles. By then it's pretty dirty a little thinner and smells like fuel. It could really use an oil cooler, but I just don't have anywhere to locate one without putting more heat into the radiator.

David
 
rjgraul said:
What kind of rattle is it? Valves, lifters etc.?
Since the late 80's most engines need no more than a 10W-30 oil due to tight tolerances in the engine. Thicker oil can actually cause other problems when trying to solve a problem.

My suggestion is try the AMSOIL RD30 (10W-30) racing oil. It is very high in zinc and phos for better wear protection and will flow faster on start up than a 20W-50 will.

If you prefer a 10W-40 then try AMSOIL AMO 10W-40 this oil is high in zinc and phos too. These two oils are man made 100% Synthetic oil not a hydrocracked refined petroluem oil that the S.A.E. mandated that can be sold as a synthetic oil when Mobil sued Castrol back in the late 1990's.

If you do not have a source to buy AMSOIL you may go to my website and click on the AMSOIL online store.

www.GetTheBestOil.com
Click to expand...

Noise soulds like hydraulic lifters/rockers and maybe a little piston slap. Mainly only happens on a cold motor that been sitting for an extended period when using the 20/50 oil. Any noise is amplified by the solid steel motor mounts, so it's not really making that much noise. It's not an OEM motor, it's all aftermarket from the oil pan to the intake manifold.

David
 
David,

I would ditch the Valvoline and I'd run 15w50 in that motor. On the cheap side Mobil 1 makes a racing oil in that is good, but Royal Purple, Amsoil, Joe Gibbs, Brad Penn, and others all make racing grade 15w50 oils. The 15w50 probably costs a couple HP but I think it would be better due to the high temps generated from the turbo vs. say 10w30. I would not run straight 20w50 in anything. As for mixing oils, I have no opinion on that one.
 
I agree with Dave. You should be running Mobil 1 at least. Joe Gibbs' oil has a lot of lubricity and is good for street/strip cars. Royal Purple also has a lot of experience with racing oils. Companies experienced with race or high performance oils tend to blend a controlled amount of detergent in their oils to prevent aerating/foaming.

Anyways, you can blend oils of the same brand to average the viscosity. If you mix two different brands, or non-synthetic with synthetic, you risk their compounds creating precipitates since each company has their own surfactants.
 
CMac89 said:
I agree with Dave. You should be running Mobil 1 at least. Joe Gibbs' oil has a lot of lubricity and is good for street/strip cars. Royal Purple also has a lot of experience with racing oils. Companies experienced with race or high performance oils tend to blend a controlled amount of detergent in their oils to prevent aerating/foaming.

Anyways, you can blend oils of the same brand to average the viscosity. If you mix two different brands, or non-synthetic with synthetic, you risk their compounds creating precipitates since each company has their own surfactants.
Click to expand...

Casey,

They are the same brand (Valvoline full synthetic race oil). I'm going to do the mix I mentioned above for this time around, but will get some of the Joe Gibbs 15-50 for the future oil changes.

I'm not married to Valvoline, but I've been using it since about 2001 in everything and haven't really had a reason to switch.

David
 
XR7 Dave said:
David,

I would ditch the Valvoline and I'd run 15w50 in that motor. On the cheap side Mobil 1 makes a racing oil in that is good, but Royal Purple, Amsoil, Joe Gibbs, Brad Penn, and others all make racing grade 15w50 oils. The 15w50 probably costs a couple HP but I think it would be better due to the high temps generated from the turbo vs. say 10w30. I would not run straight 20w50 in anything. As for mixing oils, I have no opinion on that one.
Click to expand...

Dave,

Is this the Joe Gibbs oil you are suggesting ?

http://www.amazon.com/Joe-Gibbs-Performance-15W-50-Synthetic/dp/B001J63VE6

David
 
Mobile1 10w-40 every winter. Mobil1 15w-50 every summer. Anything less in the summer and the engine won't hold what I consider acceptable pressure at hot idle.

Ira
 
I run 5w50 synthetic in the summer. Oil pressure stays at max and its good stuff for the pounding the motor sees on the road course.

Fraser
 
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