AMSOIL 10W40 runs hotter than 20W50

[kickster]

yesterday I changed the oil in my 1988 vw Jetta semi race car. The used oil was AMS 20W50. My oil temp on steady 120KM/hour was around 90-100 C

Now with 10W40 it is running closer to 110 C at same speed?
My oil pressure has also decreased from 40 psi to 35 PSI.

As I was pouring the 10W40 in my jetta it looked very thin. It was pouring like water. I changed the oil in my other car at same time but instead of 10W40 I used AMS 5W40. 5W40 looked much thicker than the 10W40. According to AMSOIL website 10W40 should be a little thicker.

 

[buster]

Was the 20w-50 the S2k version? That is heavily friction modified. The 10w-40, like the 5w-40/Delvc 1 aren't as friction modified I think. The new 5w-40 will probably hold up better although you'd need a UOA to back that up. I think it uses a newer chemistry.

 

[JohnBrowning]

Amsooils 10W40 really is not a product that most people really like! Most people that run it report oil consuption and a lot of shearing with this product. It is the only Amsoil product that I have never heard something positive about. Granted this is a very unscientific reporting of second hand information.

 

[kickster]

It was the regular 20W50 oil not the S 20W50.

I drove my Golf home tonight. Half way the oil light came up. Unlike my Jetta the golf doesnt have a pressure gauge so I dont know what the actual pressure is. before 5w40 I was using Dino 10W40 with no oil pressure problems.

I am not blaming it on oil yet. Tomorrow I will attach a gauge to read the actual pressure. It could be a sensor error!

 

[sbc350gearhead]

IIRC, like buster said, the amsoil 10w40 doesn't use any FM's and is the same as their 10w40 MC oil.