Mobile 1 15W-50 vs. Castrol Syntec 20W-50

[Autocross7]

As if this topic has not been written and replied about several times... I have been doing some reading on oil choices... I have have come down to one question...

Sythetic Mobile 1 15W-50 (as 20W is no longer available in US)

or

Castrol Syntec 20W-50

I have used Castrol Syntec in the past with no troubles, but I switched over to Mobile 1 in the RX-7 and MX-5 not long ago and I like it. However, the synthetic 20W is no longer available from Mobile (as several post suggest as does the Mobile 1 USA web site). Also, it seems Lotus now recomends 15W for the 4 pot cars as well...? but then 'the book" does state 20W?

So, I understand the 15W will flow better from cold start and the warm temp is the same, basically, but there seems to also be some discontent with the 15W-50 from mobile these days. Given that fact that i have narrowed my choice to the two above... any preferences or recomendations between the two?

Thanks,

Cameron

[Kimbers]

Cameron, please see my previous post :

Official Lotus quote from Brian Angus is as follows:

Lotus recommend the following oils:

Castrol Edge 10/60 Synth: Preferred oil

Mobil 1 15/50: If not above

Valvoline 20/50: Also if not above

Brians personal opinion was that (hope I remembered this right Brian) the 50's were fine, especially in winter when it's cold so the oil sticks just as well. However he would highly recommend 10/60 Castrol Edge when hot.

As such i have put Mobil 1 15/50 in mine now and will change it before summer to 10/60.

[Autocross7]

Thanks for the input... I did see your previous posting, but also found a number of things to read suggesting that the 10W60 Castrol was a race application oil, and possibly not so good for the street. It also appears that this is not available in the USA - at least it is not on the web site for Castrol USA. Seeing the original 20W-50 recomended oil wt, I just started thinking... again... and that is usually not such a good thing. No doubt that 15W is better at start up...

I really do not drive too hard and always let the car warm up a bit before driving at all. Even then I shift at 2500RMP until I get down the street a bit. Alabama summers typically see weeks above 95F with humidity at or above the same... but Fall fluxes wide between 70F or 80F days and sub 40F nights. Winter stays around 60F in the day and 30ishF at night... We do not have a Spring. it just jumps upto 90ish one day and summer is "on".

Thanks, again

Cameron

Edited November 2, 2007 by Autocross7