So, I am a real conservative driver and with my MCSm 08' I was getting 34-36 mpg. This was about three quarters interstate and one quarter stop and go on 91 octane. Now that I changed my oil I am only getting 33 mpg Tops. What happened? I went from the 5w-30 OEM to 0w-50 mobil 1. Do you think that the heavyier oil is effecting my mileage. Even on a road trip the other day using 91-93 octane, i still couldn't get better than 33.
Any thoughts?

 

The suggested weights for Mini are 0W30, 0w40 and 5W30. I usually use 0w30 in winter (lighter oil) and 0w40 in summer (heavier oil). Heavier oil will impact mileage somewhat but helps protect the engine more. I generally like Castrol 0w30 and Mobil 1 0w40 which are both formulated for European cars.

0W50 seems a little too heavy unless you live in the really hot climates.

 

0 is the weight of the oil the 50 is its protection agienst breaking down in high heat. if you drive conservitivley you do not need 50 you will do fine with 30-40 i use 0w-40 in my car because i auto-x it and i need my oil to stay consistant and flow through my engine fast.

 

Thanks for the responses. I decided to switch to the 0w-40 mobil 1 for the added protection. I guess I'll just use the 0w-30 Castrol when I do another oil change and see what the impact is... Or maybe the dealership will finally decide to give me my oil change. yeah right.

 

Yea 50 was way to heavy an oil for the Mini.

 

Agreed - when hot, the viscosity of a 0W-50 oil is almost twice that of a 5W-30 oil, so it's going to cost you some horsepower and fuel economy.

 

you do know the first number is the cold weight and the second number is the running temp weight right?

 

Here's a pretty good read about motor oils.
http://www.upmpg.com/tech_articles/motoroil_viscosity/

 

Once the car is warmed up, shouldn't the engine temperature be fairly constant, summer or winter?

If the engine temperature is about the same, why use a heavier oil in summer? Does a car's engine run hotter in summer? I thought the cooling system kept the operating temperature fairly constant year-round.

 

You're absolutely correct - for any particular driving style & load, the engine operating temperature is virtually constant regardless of ambient temperature.

The outside temperature makes a difference when you're starting your car and while it's warming up, so I would use the outside temperature when selecting the cold viscosity of the oil (the "0W", "5W", "10W" part).

I would base the appropriate hot viscosity (the "30", "40", "50" part) on how you're driving the car. If you're racing it or frequently towing with it, those are things that *can* raise the engine operating temperature as well as greatly increase the load on the engine, so it would make sense to use an oil with a little higher hot viscosity.

 

my running temp is about 20 less on those cold days 180 ish instead of 200 ish

 

Way to heavy. The V10 in my F-250 only takes 5w-20. 50 in a Mini is almost the same weight as what we would put in Diesels.

 

Here in Las Vegas I'm using Euro formula Mobil1 0W-40 year round in my 04' MCS. The mileage seems to have slipped a bit but during the summer the heat here is pretty close to "car hell". I use the same oil in my Porsche Caymen S in fact it's the factory fill. THe heavier vis will affect your mileage but in my opinion the extra protection is worth the slight reduction in mileage..............(MTR ON)...................mgg

 

I was considering using the Castrol synthetic oil for high mileage cars (75k+). I think it is like 10w-30 or 5w-40 I can't remember. Would that be a good iea to begin using oil designed for high mileage cars if I'm at 78k? Or, should I continue to use the OEM recommended Castrol 5w-30?
'02 R50

Btw, winter is comming on and it get's pretty cold here in KY.

 

Unless you're seeing symptoms of engine wear or seal shrinkage (routinely having to add oil between changes, puffs of blue smoke when starting up in the morning, etcetera), I don't see the need for a special oil.

Also, total mileage is a pretty arbitrary measure of an engine's age. Your engine might have less wear at 78k mile than someone else's engine at 40k miles.

 

Castrol SYNTEC 0W–30 European Formula would be a good choice. You want an oil that meets BMW's LL-01 spec. Many of the oils available in the USA don't meet it.

You want an oil that doesn't get thick at low temps, and 0W-30 is about as good as you will find for the MINI.

 

I am in AZ and it was a cool 103 degrees the other day. In the summer it can easily reach 110-115. What oil should I be using in my 03S? I run Mobile1 (dont remember which grade - however it is fully synth.). Would 0w/30 make a difference? I am trying to get my MPG back up from 23ish to high 30's on the freeway (70mph/3krpm).

 

Sorry, but you are sadly mistaken if you think just changing the weight of oil will improve mileage from the 20's to the high 30's...

Want to improve your mileage?

1.) Keep tires inflated to proper pressure.
2.) Use recommended oil weight. (here is the oil part. RTFM and follow it)
3.) change the transmission fluid
4.) change fuel filter, spark plugs, clean or replace the air filter, change the O2 sensor(s).

That's it. Then change your driving style. You will then be getting the best mileage possible. The more miles you have on those parts the worse your mileage will be. Works for any car...

 

I think that the mileage, if it drops from high 30s to 23 mpg, is a sign of not only maintenance needs (which is a good thing that richardperry suggests), but perhaps something that could be wrong with the car.

In AZ especially for the summer, I would tend toward higher weight oils just to protect the engine.

 

Also, I don't think a first-generation 'S' was ever good for high 30's on the freeway (or it may just be the extra drag from my convertible top and the fact that my mileage drops like a stone over about 75 MPH.)

In addition to what's been mentioned before, I would check out your supercharger belt. If it's gotten worn, glazed or stretched you'll lose boost and efficiency.

My around-town economy has dropped from about 26 MPG to 23 MPG or so over the past 3-1/2 years. I'm following the OBC service recommendations (other than oil changes), so as a result, I've got over 70k miles on the original plugs, wires, and supercharger belt. They'll all come due for replacement in the next 2000 miles, so I'm curious to see how much of a difference it makes in my fuel economy.

 

1.) Keep tires inflated to proper pressure.
New Potenza tires with 25k on them. Pressure check, balance, alignment and rotation done last week.
2.) Use recommended oil weight. (here is the oil part. RTFM and follow it)
Not sure what RTFM means but if its anything like "read the F*#^%!ng manual" then thanks for your input. However such a response is neither needed nor is it appreciated. Besides, as you continue to read among the many posts, you will find that there are better things than BMW's "recommended" items. This goes for especially for oil. Just because BMW recommends Castrol doesn't mean its the best thing to put in your engine.
3.) change the transmission fluid.
Did that about 20k miles ago and used Redline.
4.) change fuel filter, spark plugs, clean or replace the air filter, change the O2 sensor(s).
Only thing left is the O2 sensor. The rest are changed regularly.

 

I used to get a hair more than 460 miles a tank full at 70 mph @ 3k rpms. I know this cause I traveled between Phx and Tucson everyday for nearly a year. I think you might be right about the S-belt. It's long overdue for a fluid change with 70k miles on my new S-charger. Taking the front end apart is not my idea of fun. However, it beats paying the stealership to do it. Maybe I will get a reduction pulley while I am at it.

 

i noticed that as well. I bought a couple cases of 0w-50 Mobile1 from a local guy who didnt need em, and compared to the stock oil it did hender the mileage by a few.

 

I just picked up some Mobil1 0w-30. Maybe before the next oil change I will add some Seafoam to it and run it a bit.

 

yup cant hurt. the 0-30 should also be just fine. I wasnt sure if they did the European spec in 0w-30... didnt research all that much though. there are already a few good threads somewhere on here with whats what lol