Which synthetic would be recommended? Amsoil,Mobil1,Castrol syntec,Royal purple?

[mattd1979]

I'm going to be changing my oil today and I have been using M1 10w30. I read about the 0w40 M1 and Castrol syntec 0w30 is what I would get if I wanted true synthetic oil. I was wondering how the 0w40 would be in the summer here in florida? I have a mechanical oil pressure gauge in my car so I can see where the pressure is. When I first start the car up in the mornings, it is at 45 psi cold. When it warms up, it is just under 20psi and on the interstate at 70MPH is is at 73psi. with outside temps at 73 degrees. This is with the M1 10w30. What do you think it would be with 0w40? I was also thinking about Amsoil and Royal Purple synthetics. I can get both of those at either Napa or Advance Autoparts I believe. What do you think about those brands?

[maxnix]

Any should work well if you change often enough. It is condensation, combustion by products and heat that primarily break down oil and its additives.
Modified by maxnix at 8:38 PM 2/18/2009

[Q45tech]

Why not do some tests with various oils and filters? As I pointed out only hot idle [>73F] with a brand new oil and filter is the critical low PSI point.As oil ages it gets thicker thus the idle psi increases.

Remember the first number is the 32F thickness and the final number is the 212F thinness.

[qship96]

I would vote for Mobil 1 ow-40 as one of the best oils at ANY price= certainly way, way better than any other grade of mobil 1 oils, and better than Royal Purple, and most versions of Amsoil.

The problem with Amsoil, other than their pyramid marketing and overzealous cheerleaders, is they produce so many different oils at different price/quality points, their lineup is confusing to many people.Ther "xl7500" line is just a average group 3 based "synthetic", while their top tier SSO is a true,group 4 real full synthetic oil and priced like one{over $12 per qt}

M10w-40 is a top shelf true synthetic oil easily found locally and a great weight for the Q.

[Q45tech]

Why not do some tests with various oils and filters? As I pointed out only hot idle [>73F] with a brand new oil and filter is the critical low PSI point.As oil ages it gets thicker thus the idle psi increases.

Remember the first number is the 32F thickness and the final number is the 212F thinness.

Each number is a range not an absolute number so each brand can have a +-5% variance whereas w40 is ~~ 25% thicker than w30 so the pressure might increase by ~~ 10-25% at idle that could be 2-5 psi. Each brand will be different.

"Only about .001" of wear in the main bearings can reduce oil pressure up to 20%! "

[mattd1979]

For those that said that Mobil1 0w40 oil was imported from Germany and had the word "Imported from Germany" on the back of the bottle, it is no longer there. I looked for it everywhere on the bottle but couldn't find it. I know that it used to be on the back of the bottle the time before when I was looking. About 8 months had past during that time. I don't know if it is still imported from Germany or the US has started manufacturing it.



P.S.I noticed that at idle when first started, the oil pressure is at 60 psi. When the speed is increased to 4,000, it will almost peg the gauge. After it has warmed up, it is at around 8 psi and when increased to 4,000, it reads 75 psi. It starts reading 70 psi at 2500 rpm I believe. The gauge is a SunPro and it reads in increments of 25 psi. It reads 0,25,50,75,100.

Modified by mattd1979 at 10:13 PM 2/18/2009
Modified by mattd1979 at 10:14 PM 2/18/2009

[qship96]

You are confusing the 2 oils- it is{was} Castrol Syntec 0w-30 that was the elusive made in Germany formula that was a true group 4 synthetic oil{all other castrol syntec versions are group 3 processed mineral oil. Mobil 1 in the 0w-40 has always been a true group 4 synthetic, regardless of country of manufacture.

You need a much more accurate/finer resolution pressure gauge to double check hot oil pressure to rule out a potential problem.

[Jesda]

That's reassuring info. The sticker on my engine says to use M1 0w40.

[Q45tech]

The factory absolute MINIMUM for HOT IDLE [750 rpm] is 14 PSI.Anything lower with a xW30 oil weight indicates excessive bearing wear!

"After it has warmed up, it is at around 8 psi "

Be sure to read with an accurate professional gauge with 1.0 psi increments.

[mattd1979]

I am updating what I said in my last post about the oil pressure readings. This morning I made sure to read the gauge after I started it and I noticed that at idle, it was reading 50 psi. When I increased the speed to 3000 rpm, it was almost at 100 pai. After I had driven it for 30 minutes, I noticed that at idle, it was around 10 from what I could figure, and it would climb t0 65 psi when I increased rpm to 2000, and when I increased to 3000 rpm, it was reading 75 psi. I will have to find a more accurate gauge to get more precise readings. I just figured that what I have in there now is far better then an idiot light. This is the same gauge that I had installed before my other engine lost oil pressure. It saved the motor. That is, when I noticed that the oil pressure would not climb above 45 psi when it warmed up, I stopped driving the car before I had severe engine damage and parked it until I could figure out what to do. I ended up putting another engine in it and I kept the one, thinking that maybe the oil pump may have gone bad. I figured someday down the road, I would try to revive it.

[qship96]

Check crank pully bolt torque.

[mattd1979]

Are you refering to my old engine? If so, I did that and it was to specs. I was told to check that when I first posted about the oil pressure drop which I believe was a year or more ago. My current engine is doing great, aside from the occasional failing injector.