What oil and octane fuel do you use?

[TimKninja]

10w40 , and 91.

Can anyone tell me if the m50 is meant to take 91 or not?

[Jaxx_]

15w50 mobil 1 year round.

93 all day, because of the megasquirt tune.

[bastianshaw]

It doesn't damage your cat?

What would damage my cat?

Running synthetic oil is pointless in a stock m20, you still have to change the filter every 3k miles so unless you want to put your old synthetic oil back in for another ~2k miles it seems to me to be a waste of money YMMV

VR1 has high deposits of zddp (google and learn) and the m20 likes heavy oil hence the 20w-50

Its totally fine to run a higher octane, the only danger is running too low an octane ; this must be taken with in reason

[Emre]

What would damage my cat?

High levels of ZDDP are good for valvetrain wear (especially with flat tappets), but not so good for cats. That's the main reason why levels of ZDDP have been going down in modern motor oils. Even diesel oils have been affected.

Sacrificing engine life for cat life seems stupid to me, but there's no point in arguing logic with the EPA.

[flyboyx]

i always use shell rotella T full synthetic. that is what i use in my diesel truck, my gf's car, my s52 swapped cabrio, my tractor, my lawn mower, my boat...... this is a fantastic oil for the price. if it is good enough for a diesel engine, it is certainly good enough for my car. other than the cabrio(stupid paper filter cartrige) i ALWAYS buy the best filter that i can find. usually fram tough guard or extended guard. this really makes a bid difference in how many miles the oil stays nice and clean/clear.

fuel: just the standard 91 octane.

[Raxe]

Too high of an octane is bad for your exhaust and will melt your cat (if you have one.)

The right octane is harmless. Stick with that.

91 for me as I'm chipped and 20w50 right now. Will switch to 5w30 TOTAL after my rebuild.

[CHIF8008]

87 octane for the eta

10W30

[Emre]

i always use shell rotella T full synthetic.

I don't want to open up a huge can of worms here, but like Valvoline VR1, Mobil 1, Castrol Syntec, and most other "synthetic" oils, Rotella T6 uses a Group III base stock. Not that it's a bad oil, but most people feel you can't honestly refer to an oil as "full synthetic" unless it uses a Group IV base stock (like Amsoil and Red Line) or a Group V base stock (like Motul 300V and Torco SR5).

Also, Rotella T6 no longer has a high ZDDP content, if that's important to you.

if it is good enough for a diesel engine, it is certainly good enough for my car.

Diesel oils are designed to deal with very different operating conditions than, say, an S14 race engine. I also use diesel oils in my 560SL, which has an old, dirty, low-revving 5.6L V8 under the hood. Diesel oil may be a good match for an M20 with an auto gearbox or 325e that's never going be be revved past 3.5K rpm, but I'm not sure it's the best choice for an E30 that gets run hard.

i ALWAYS buy the best filter that i can find. usually fram tough guard or extended guard.

I probably sound like a downer, but Fram filters are generally considered to be among the worst with the lowest quality filter element. The only exception are the HP1 and HP4 race filters, which have a totally different construction.

If you want a great filter that will continue to work well for very long drain intervals, try Wix. If you can't find Wix, then Purolator and Mobil 1 are not bad.

[freeride53]

1991 M42 gets 10W40 Chevron & 91 Octane.
Wish California had 93 Octane available..

[stamar]

if you have a m42 or an m50 you want to use that vr1 stuff, or rotella diesel oil, with zinc additives.

Those are the engines that fall apart with modern oil.

[CHIF8008]

Fram filters suck butt

[smooth]

how is my reference NOT relevant? YOU where the one who pointed out the FACTORY OWNERS MANUAL says to run 87 so i just pointed out you cant go by what the manufacture says all the time as there are other factors at hand.
but i guess you believe everything you read right
you seem a bit mad, whats up with that?

Technically, I go by the Bentley manual. But in this case it mirrors the BMW manual so my opinion to go by that unless you have a good reason otherwise is the right advice.

Claiming performance gains from using higher octane is poor advice. Using your brother's car, a non-e30 with unknown engine management, as an example of not following BMW's manual about our e30's is irrelevant.

Clearly there are times when one should deviate from the owner's manual. I posted that I have to run 91 octane because I have a performance chip. That's not because the fuel gives me more performance it's because the timing is different and the higher octane is necessary so the detonation is correct.

My father and grandfather built up some '40s cruisers and I believe at least one went through a 12v conversion. If they followed Plymouth's manual about the electrical something would blow up...so clearly some common sense should be used when reading my post. If you want to just argue, then that's fine, but don't pin in me being angry or whatever because that's not even remotely close to reality.

BMW engineers designed our timing to run on 87 octane. Unless you've changed something running a higher octane is going to either do nothing or cause an issue. You will not get better performance just by using a higher octane gas in your stock e30. Your example of your brother was not about his experience with an e30 so it's not relevant to a thread about what e30 owners use or should use in our M20 engines.

Similarly, with engine oil, new oil technology has progressed since our engines were built. But unless you know what you're doing it's safer and best to follow the owner's manual.

Someone else mentioned that he didn't understand why engine longevity should be maximized at the expense of cats. The main reason is that catalytic converters are simple to replace and they aren't more expensive than a proper engine rebuild. A factory cat costs around $1500 but it'll last another 20 years. A proper rebuild will also last another 20 years but it'll cost about twice the cat.

[Emre]

if you have a m42 or an m50 you want to use that vr1 stuff, or rotella diesel oil, with zinc additives.

As I posted above, Rotella doesn't have much ZDDP anymore. Oils with documented high ZDDP include:

Kendall GT1 (in 20W-50 only)
Brad Penn GT1
Mobil 1 (in 15W-50 only)
Amsoil Dominator
Valvoline VR1

[Emre]

Someone else mentioned that he didn't understand why engine longevity should be maximized at the expense of cats. The main reason is that catalytic converters are simple to replace and they aren't more expensive than a proper engine rebuild.

If you're referring to me, I said the exact opposite. Read post #34 above.

[Adrian_Visser]

how is my reference NOT relevant? YOU where the one who pointed out the FACTORY OWNERS MANUAL says to run 87 so i just pointed out you cant go by what the manufacture says all the time as there are other factors at hand.
but i guess you believe everything you read right
you seem a bit mad, whats up with that?

Your reference is invalid because the engine management systems on an e30 and a c6 'vette are completely different.

Most newer vehicle's ECUs adjust ignition timing using the knock sensors thereby getting the best performance out of the fuel that is in the tank. An e30's 20+ year old DME doesn't attempt to adapt ignition timing for different fuels. It sticks with whatever the EEPROM chip tells it to.

So running 94 octane in your stock m20 with stock chip will result in no power gains, it might as mentioned before clean your intake valves better than lower grade fuel though which could make it run better.