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best oil ?

4K views 39 replies 25 participants last post by  ambystom01 
#1 ·
looking to daily my car all through winter except when it snows.... and lately ive noticed my oil pressure is sky high when i start it cold.... since the temps have been low.... what oil and weight should i use through winter to keep viscosity on the lower side. yes i know letting the car warm up solves the problem. but id still like to run a better winter oil. Also looking to replace the tranny and diff fluid... any ideas on the brand, type, and weight for those?
 
#2 ·
Redline 75w90 for the diff and gearbox. That's a must.

As far as engine oil weight, I haven't had any trouble with my Mobil 10w30 on cold days. I also need to replace my oil pressure sender, so there could be a better weight to use. lol
 
#5 ·
done my research. and what you say makes sense. im going to do gl5 for the diff and gl4 for the tranny. thanks a bunch
 
#3 ·
Is too much pressure really a bad thing? I use 10W-40 and cold oil psi gets pretty high. Better than too low in my opinion. I think I need to go down to 30 as oil temps never get hot enough when cruising (won't reach 200 degrees unless I am applying more load and revving at 4k+
 
#4 ·
yes it can be. after reaching 3k+ rpms im at 90psi+ and that too long can blow gaskets. yes your right in low pressure is bad. but im looking for a more consistent medium for the winter.
 
#10 · (Edited)
It seems the two most highly regarded motor oils at Miata.net, where they take such matters very seriously, are Mobil 1 OW-40 and fully synthetic Shell Rotella-T 5W-40. The 0W-40 is expensive and sometimes hard to find; the Rotella-T 5W-40 can usually be found pretty reasonably at Walmart. I use the Rotella-T in everything I own.

As for Tranny fluid, again the most highly regarded at Miata.net is Ford Motorcraft Fully Synthetic Part XT-M5-QS Transmission fluid. Redline is a distant second, though it's prized for its toughness. Here's a link if you want to investigate further:

http://forum.miata.net/vb/showthread.php?t=270393
 
#36 ·
I have Motorcraft in my transmission. I am really not sure I like it to be honest. I mean, my experience seems to match others where at higher temperatures shifting is smoother but it is not consistent and still rather notchy. I may just try the GM Synchromesh or Redline stuff next time around. I did have Redline MT90 in the 2000 Celica I used to own and it made a world of difference (but of course, that is sort of apples and oranges ;) ).
 
#11 ·
I run 0w-30 Castrol. Its great, otherwise its really going to be personal pref. try the bobistheoilguy forum.

As for transmission and diff...you have to use gl5 in the diff. don't use anything else. Personally i just use 75w90 redline gear oil. its orange colored and works like a charm.

Motorcraft synthetic was suggested to me (for the transmission) and it has been way beyond my expectations. The shifting instantly improved; its smoother, easier, and has a definite, solid feeling when going into gear. Easily worth the extra penny you spend, plus how often are you really going to change your tranny fluid? once every 2 years? so it really comes down to spending an extra $18 (compared to redline MT-90) every two years.

PS if you buy your motorcraft here, its only a $4 a bottle diff (2 bottles is what you need) making the difference practically negligible. Make sure you buy Motorcraft with part number XT-M5-QS because they make other types of transmission fluids which are much cheaper.
 
#14 ·
i run 5w40 when cold and 10w40 when its hot. w40 is turbo diesel oil and is better for your engine has a lot more minerals in it and helps strengthen you engine.
 
#16 ·
I guess "cheap" is a relative term?

fwiw Mobil 1 is the best oil I've used to date
 
#33 · (Edited)
Mobil 1 0W40. Five quarts and an M1-110 oil filter (I use the larger one, I think M1-108 is the usual one for the NB) are often available at O'Reilly, Autozone et.c. as a deal for around $30. Fair price for excellent oil imo.

As I am in Arizona and in gets ungodly hot in the summer, the 0W40 perfoms great, especially at the track.

Now, I have had several oil analyses done (Blackstone labs), the last one was exceptionally good. 5682 miles on Mobil 1 0W40, three days at a track (AAS & RFR) including several long trips but they suggested I could easily have changed at 7500 miles. No signs of wear, plenty of additives left. No topping, up either :)
 
#40 ·
I use Rotella 0w40 for both my cars and it seems to hold up quite nicely. Oil pressure is very consistent and stable and oil temps have never gone above 250 even at the track (I'm still using the stock oil cooler with no cooling mods). Whenever I change it, it comes out looking surprisingly clean. If I can remember, I'll get an analysis done after my next oil change. I'll probably switch my drivetrain fluids to Motul come spring.
 
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