SAPPER

iTrader: (10)

Always talk about oils, Why is it everyone despises or passes off Amsoil. How many of you know that it's the first synthetic oil ever designed in 1972 and has the largest R&D of any oil company. NO other company tests their oils against other brands in so many wide ranges of tests.
Granted, Amsoil oils many not be #1 in every test but if it's not the best in a particular test, it will be in the top 3 of the 8 to 10 oils tested.
Also, even the prices are very comparable if not much less than all the other so-called, race oils.

OP, your engine builder should tell you what oil viscosity you'll need based on the clearances in your engine. If they are all within stock, the Improved Racing is correct based on oil temps. Stick with your cold weight being 5W but there's nothing wrong with using 5w50 or 60.
Even the 5.0 coyote runs a 5w50 because ford knew they would see high prolonged temps.

pantera_efi

iTrader: (1)

Hi Sapper, I AGREE with your report.
Amsoil includes ADDITIVES that the others do not formulate to increase engine life.

RACING engines run TIGHT bearing clearance .002" or less as often specified.
The Oil Viscosity needs to be correct allowing Oil Flow in the bearing area to REMOVE HEAT.
The Oil Pressure needs to be correct, great enough to transfer that heat into the oil.
The FACT that Low Viscosity oil will have a much faster sump return rate should be considered.

Lance

ImprovedRacing

Just keep in mind the the "5W" part of a 5W30 is not the same as a 5W50. It's a little misleading.

For example:

Mobil 1 5W30:
Viscosity, @ 40ºC, cSt (ASTM D445) 61.7
Viscosity @ 100ºC, cSt (ASTM D445) 11.0

Mobil 1 5W50:
Viscosity @ 40ºC, cSt (ASTM D445) 104.3
Viscosity @ 100ºC, cSt (ASTM D445) 17.1

Note that at 40ºC, the 5W50 is actually 70% thicker than 5W30.

So at startup this oil will be much more viscous, even though they have the same "5W" winter rating.

mikedamageinc

iTrader: (49)

Run the stuff your engine was designed to run, in the case of most street engines its 5w-30. Unless you have a specific need, in which case you will already know, like engine builder told you or if you know your stuff runs at 300 degrees. If you just run something thicker it will not fix anything and could cause problems.

Also get an oil temp gauge to see what you are running at, then decide if you need a cooler or to change weights. Do used oil analysis too so you know if it is breaking down.

You also cant go by the whole "I've been using this brand for this long and its great". So you engine hasn't blown up? great, you can not change the oil period and it will run way longer than the 3k/5k/etc change interval. Most people could put some good ol' wally world supertech fluid in their car and never tell a difference, as long as it gets changed it will run for a long time.

That being said, I've had great results (Blackstone used oil analysis) with Mobil 1 euro 0w-40 and Redline 5w-30 for street/auto x/track days. The viscosity rating has a range and these are both very close as the Mobil is on the low end of the 40 scale and Redline is on the high end of the 30 scale. You can read all about oil until your brain turns to mush on Bob's the oil guy forum.

Zmg00camaross

iTrader: (11)

I like to run 5w40 diesel oil. My engine seen anything from 0w30 to 5w40. Mid summer racing i am sure oil temp is getting up there.

Dian

sorry to revive this, but its simply wrong to use diesel oil:

the additive package is completely different, part of it is not needed and it lacks a part essential for a gasoline engine.

Zmg00camaross

iTrader: (11)

What is the essential part that diesel oil is lacking?

Dian

defoamants, antioxidants, acid neutralisers. gas oils also need more shear resistance and doesnt need as much dispersants because there is not as much soot.

if you put diesel oil into a high reving engige it might look like cappuccino after a short while.