what makes an engine more fuel efficient?

[christophbmw]

Synthetic lubricants, as appropriate, in the gearbox and the diff.
Protects better, lower friction (better fuel economy), lasts longer. But costs more.

You can run higher pressure in your tires

synthetic not recomended on the syncros of the getrag tranny, and its also not recomended in the engine.....dont know about the diff though, higher quality fluids are only good for like 1-2mpg at the very most.

High quality petrol (Cheveron, 76 and shell to name a few) drastically help. Mythbusters on disicovery saw a 3 mpg difference by using 76 versus a mom and pop fuel station.....if you do the math its worth the extra price the higher end gas stations charge :cool:.

[tjts1]

+1....except, your running 0W-30 in the winter :eek:, what effects does this have on the engine ?....ive never seen anybody run that stuff in the M42.

M1 0w30 to be exact. If you look up the CST specs on BITOG, at 100c its just below the cusp between 30 and 40 weight but I prefer the 0w over 5w weight for cold morning start ups and I live in California... LOL.
http://www.bobistheoilguy.com/forums/ubbthreads.php?ubb=showflat&Number=1104890
http://www.infineum.com/information/api-viscosity-2004.html

ps, i think you meant to say cone filter instead of "cold air" because the M42 already has a "cold air" intake from the factory :rolleyes:.

I keep reading the same response on every E30 forum: "the car already has a cold air intake". I don't know where the myth got started but it couldn't be further from the truth. The E30/M42 repair manual clearly states that the stock intake operating temperature is 122-158f.
http://farm4.static.flickr.com/3104/2451663089_638bf16fe5_o.jpg
I tested and confirmed this by placing the outside temperature sensor inside lower airbox. The temp inside the airbox varied between 10f above ambient on the freeway to 40f above ambient in stop and go driving.
No, I didn't use a cone filter. Theres nothing wrong with the stock airbox. Just the intake to the airbox need to be changed.
http://www.m42club.com/forums/showthread.php?t=5561

synthetic not recomended on the syncros of the getrag tranny, and its also not recomended in the engine.....dont know about the diff though,

Not recommended by who? I would be interested to see a source for that information because I just filled my tranny redline MTL, redline 75w90 in the diff and Rotella 5w40 in the engine. I have never heard of synthetic oil somehow damaging a BMW engine or transmission.

higher quality fluids are only good for like 1-2mpg at the very most.

With a 14 gallon tank thats an extra 14-28 miles per fillup or 3-6% better fuel economy if you average 30mpg. At $4/gallon gas, synthetic fluids will pay for themselves many times over in the span of one oil change.

High quality petrol (Cheveron, 76 and shell to name a few) drastically help. Mythbusters on discovery saw a 3 mpg difference by using 76 versus a mom and pop fuel station.....if you do the math its worth the extra price the higher end gas stations charge :cool:.

I must've missed that episode.
Every gas station in my area be it Arco, Chevron, Shell or the local mom and pop get their gas out of the same truck coming from the same refinery in Richmond. Unless the gas was somehow contaminated with water, there is absolutely no difference from gas station to gas station in the same area. The additives and seasonal formulation of gasoline is dictated by the EPA under federal law. Any perceived difference between brand name additives already in the gasoline like "Techron" or shell "Drive Clean" is simply advertising hype. I've never seen any drastic fuel economy difference with one brand of gas over another.
http://www.epa.gov/otaq/fuels.htm

cheers
Justin

[colin86325]

synthetic not recomended on the syncros of the getrag tranny, and its also not recomended in the engine.....dont know about the diff though, higher quality fluids are only good for like 1-2mpg at the very most.

Use the type of fluid indicated by the sticker on your tranny:  either oil or ATF.
Synthetic varieties of both types of fluids exist.

[christophbmw]

M1 0w30 to be exact. If you look up the CST specs on BITOG, at 100c its just below the cusp between 30 and 40 weight but I prefer the 0w over 5w weight for cold morning start ups and I live in California... LOL.
http://www.bobistheoilguy.com/forums/ubbthreads.php?ubb=showflat&Number=1104890
http://www.infineum.com/information/api-viscosity-2004.html

I keep reading the same response on every E30 forum: "the car already has a cold air intake". I don't know where the myth got started but it couldn't be further from the truth. The E30/M42 repair manual clearly states that the stock intake operating temperature is 122-158f.
http://farm4.static.flickr.com/3104/2451663089_638bf16fe5_o.jpg
I tested and confirmed this by placing the outside temperature sensor inside lower airbox. The temp inside the airbox varied between 10f above ambient on the freeway to 40f above ambient in stop and go driving.
No, I didn't use a cone filter. Theres nothing wrong with the stock airbox. Just the intake to the airbox need to be changed.
http://www.m42club.com/forums/showthread.php?t=5561

Not recommended by who? I would be interested to see a source for that information because I just filled my tranny redline MTL, redline 75w90 in the diff and Rotella 5w40 in the engine. I have never heard of synthetic oil somehow damaging a BMW engine or transmission.

With a 14 gallon tank thats an extra 14-28 miles per fillup or 3-6% better fuel economy if you average 30mpg. At $4/gallon gas, synthetic fluids will pay for themselves many times over in the span of one oil change.

I must've missed that episode.
Every gas station in my area be it Arco, Chevron, Shell or the local mom and pop get their gas out of the same truck coming from the same refinery in Richmond. Unless the gas was somehow contaminated with water, there is absolutely no difference from gas station to gas station in the same area. The additives and seasonal formulation of gasoline is dictated by the EPA under federal law. Any perceived difference between brand name additives already in the gasoline like "Techron" or shell "Drive Clean" is simply advertising hype. I've never seen any drastic fuel economy difference with one brand of gas over another.
http://www.epa.gov/otaq/fuels.htm

cheers
Justin

im not saying sythetic fluids are bad because they are expensive, i use crude oil that is far more expensive than most sythetics (Swepco oil), its just that they are not recomended for certain things, the tranny being one of them, the way the syncros are set up the outer ring of the syncro will wear ALOT faster with the use of sythetic syncros.....if you dont believe you will when you have to pull your tranny for a rebuild (trust me ive seen it happen MANY times when enthusiast drivers of #21, and E30's put synthetic in their trannys'. But then again if you double-clutch and arent as hard on the syncros then your tranny may last, im just putting in my two cents from my personal experience.

Also have you ever worked at a gas station? All fuels are NOT the same, if they come from the same truck in your area then whoever is in charge of their gas station are crooks. Cheveron comes from a Chevron truck, 76 comes from 76 truck....or at least in my area.....not to mention the color is clearly a different shade from gas station to gas station. You should download the myth busters episode, it was filmed in your neck of the woods.....may be a real eye-opener.

As for everything else you seem right, i never knew the temp inside the airbox of our cars.....i geuss i cant call it a cold air intake anymore .

[tjts1]

Well I guess I'll keep an eye on my transmission then but are you sure the failure happened because the fluid was synthetic and it wasn't simply the wrong kind of oil? Our transmissions specify ATF but I've seen people use all sorts of things like GL-5 gear oil or engine oil both synth and dino juice. Even my choice to use MTL is somewhat problematic but it shifts beautifully with it. It even lets me down shift from second to first at 10 mph without any resistance, something I couldn't do before.

[christophbmw]

Well I guess I'll keep an eye on my transmission then but are you sure the failure happened because the fluid was synthetic and it wasn't simply the wrong kind of oil? Our transmissions specify ATF but I've seen people use all sorts of things like GL-5 gear oil or engine oil both synth and dino juice. Even my choice to use MTL is somewhat problematic but it shifts beautifully with it. It even lets me down shift from second to first at 10 mph without any resistance, something I couldn't do before.

im not excactly sure it was the fluid, but three out of the four tranny's ive seen with bad syncro's had MTL in them, could be coincidence since the syncro's do wear out at about 200K, but either way i will only put fluids in my car that the engineers over at Munich, Germany say to put in it. Why compromise, the tranny works fine with high quality ATF.

[tjts1]

Well if I still own this car 40 k miles from now, I'll worry about it then. More likely than not, I'll probably be driving something completely differed by then.

[PaulC]

Regarding synchro wear with synthetic gear oil. AFAIK, it can be too slippery and the synchros won't engage (or grip) properly and will 'burn', resulting in toasted synchros. Also, some trannies have specific metals which don't react well with certain additives. Swepco has a good reputation in many circles. Another oil I've heard good things about is Lubrication Engineers.

Regarding Redline, I know of three transmission shops who will charge you extra to clean out your 'box if you've been running it. Supposedly, its due to high sulfur content which gunks up in hard to reach places. Redline claims its only the Shockproof formula which is 'specific' and that they resolved this issue years ago. I dunno.

I've used Redline in the past and it feels great, especially in winter. With a street car I now lean towards dino juice in the gearbox and diff, because of the potential work and cost involved with a rebuild. Thats just my opinion though. YMMV.

[christophbmw]

........double clutch.......my old tranny had shot syncro's so it was nessasary, now i swear by it to prolong tranny life.