Fluid change questions
 

I'm going to change my oil, diff, and trans oil in the next 3 weeks. Just have a few questions for each (I just bought the car a few weeks ago and it didn't come with a manual or anything. Also, if there's an online manual or how to guide, please let me know):

OIL: What brand are you guys using? I was thinking Valvoline MaxLife, I have 107K right now. Also, what weight?

DIFF: I found the "How To" guide and it seems simple enough. What brand and weight should I get?

TRANS: Should I even bother changing the fluid at this point? If so, is it just a simple drain/fill plug? How much? What brand and weight?

Thanks ahead of time!

Def do all 3. Trans and dif are not needed often so might as well spend the extra on the good stuff.

Oil: 6 quarts 10W20 Motorcraft semi-synthetic or Mobil1

Diff: 2 quarts Royal Purple Max Gear 75W90, already has friction modifier in it (have to add friction modifier if you get regular rear end fluid)

Trans: 3.2 quarts Royal Purple SyncroMesh (There is a fill plug and a drain plug on the tranny, drain it then pull the fill plug out and disconnect the shifter and fill from the inside of the car until it starts dripping from the fill plug. then put the plug and shifter back in. (do 3 quarts RP and then whatever else you have handy or is cheap)

Definitely 10w20? And not a full syn oil?

The How To I read on the diff had him adding some LSD additive I believe WiTH RP. You're saying not necessary?

Is there a how to on the tranny? I've never heard about doing it like that.

I would definatly stay away from Mobil 1 after reading about recent downgrades in their base stocks. I would run 5w30 winter and 10w30 summer for pennsylvania. If you change every 3-5k miles you will be fine with motorcraft synthetic blend. Penzoil ultra platinum seems to getting top end reviews as well. I run Valvoline synpower 10w30.

Yeah, I heard about Mobil 1. What a shame. Someone was saying that their only real syn is their Extended Performance, but who knows.

Would it be bad to do 5w30 year round?

Mobil has never "downgraded" the base stock for M1, this was a completely unfounded rumor that seems to have sprung out of their changing the formula a few years ago--the key word being "changing", not downgrading.

In fact it has been changed several times, one would hope that in the 36 years it has been on the market it would be as technology and knowledge advance.

from their FAQ:
All "100% synthetic" motor oils made primarily of Group IV base stocks contain carrier oils--which may be Group III cracked dino oils, or Group V synthetics. The carrier oils are necessary because PAOs are fully saturated oils.

This makes them great at resisting chemical breakdown, however it also means that the additives needed (anti-wear/foaming/oxidant, friction modifers, etc.) to make a good engine oil do not disperse well into the PAO--the carrier oils do just as the name implies and "carry" the additives within the blended oil.

Mobil chose to use a Group III oil as the carrier and because they do not hide their formulations, like most of the snake oil vendors, they (the SOVs) used that fact as a way to promote their products by harping about M1 not being a "real" synthetic oil and selling the reformulation (packaged as hardcore "FUD factor") as a "downgrade", to an uneducated public

The reality is that the Group III oils have a number of properties that make them preferable to the Group V "esters", and I suspect that the SOVs use Group III carriers in their products as well...

Ford calls for 5w-20 motor oil, 75w-140 synthetic gear oil.

yeah my bad i meant 5w20 dunno where i got 10w. sorry about that. ive always been told 75w90 at the auto stores. hmm...

just read on american muscle 75w90 for 79-04 75w140 for 05 and up...

Hmm... my diff has a metal tag on it that says 75w-140 synthetic, and thats what I've always been told?