Not joined yet? Register for free and enjoy features such as alerts, private messaging and viewing latest posts and topics.

Mixing engine Oils

Specific discussion about the E89 2009 Z4 (sDrive35is, sDrive35i, sDrive30i, sDrive23i)
Post Reply
User avatar
benv6
Member
Member
Posts: 418
Joined: Thu Apr 30, 2015 2:28 pm
Location: Berkshire

Mixing engine Oils

Post by benv6 » Mon Apr 17, 2017 1:16 pm

I am due for a service and I will be going for the 5w40 instead of the 0w30 (Castrol Edge)

My question is that I do have about 2l some 0w30 left from last service, and was wondering if I can mix it with the new 5w40 ?
Now: BMW 335D Touring
Previous: 435D Coupe, BMW Z4 E89 35i, BMW Z4 E85 2.0, BMW E46 330CI

ImageImage

User avatar
Mad Professor
Member
Member
Posts: 611
Joined: Sat Dec 20, 2014 7:38 pm

Mixing engine Oils

Post by Mad Professor » Mon Apr 17, 2017 1:44 pm

Wont do any harm IMHO as long as both are fully synth
Present : 987 Box
Past history : ,Z4MR ,Cat HPC evo , XKR , Eunos VR , Eunos VS, Westie S8 ,TVR S2 , S54 Z3MR, SL500 , TVR Wedge 4.6 , Cat Xflow , Saab 900 Turbo ,Cat VXE ,Cat BDR, Cat Twincam , Elan S3 , Haldane Healey, Lancia HF turbo

User avatar
ronk
Lifer
Lifer
Posts: 14199
Joined: Tue Feb 24, 2009 11:50 am
Location: Durham

Mixing engine Oils

Post by ronk » Mon Apr 17, 2017 2:30 pm

Why do you want to go 5w Ben?
You don't stop playing when you get old - You get old when you stop playing!
So I bought a 35is with all the toys to play with. :thumbsup:

User avatar
Smartbear
Lifer
Lifer
Posts: 13685
Joined: Wed Feb 05, 2014 6:54 pm
Location: a barn in Somerset

Mixing engine Oils

Post by Smartbear » Mon Apr 17, 2017 2:36 pm

Hi, as the mad professor says-its fine as long as they are both synthetic & the grade difference wont matter :thumbsup:
Rob
Image

e89 Sdrive 20i, plenty of mumbo & good economy-the thinking bears z4
e89 Sdrive 30i, this ones busted, pass me another...
e85 3.0si sold

User avatar
benv6
Member
Member
Posts: 418
Joined: Thu Apr 30, 2015 2:28 pm
Location: Berkshire

Mixing engine Oils

Post by benv6 » Mon Apr 17, 2017 2:52 pm

ronk wrote: Mon Apr 17, 2017 2:30 pm Why do you want to go 5w Ben?
I want to see what would be the MPG difference, I heard you would get better MPG with 5w40 :)
Now: BMW 335D Touring
Previous: 435D Coupe, BMW Z4 E89 35i, BMW Z4 E85 2.0, BMW E46 330CI

ImageImage

User avatar
cj10jeeper
Lifer
Lifer
Posts: 17846
Joined: Fri Jun 22, 2007 11:50 am
Location: Lichfield, England

Mixing engine Oils

Post by cj10jeeper » Mon Apr 17, 2017 4:03 pm

Real bad idea to just change oil grades. Manufacturers specify oils grade and other factors for very good reason
Jaguar F-Type 3.0 Supercharged V6 S, Stratus Grey, LSD, Active Exhaust, CF wheels, Performance brakes, Sports seats and mods ongoing
Gone but not forgotten Z4 3.0i SE Roadster ///M front, Red ///M leather seats, Aero sills

User avatar
Smartbear
Lifer
Lifer
Posts: 13685
Joined: Wed Feb 05, 2014 6:54 pm
Location: a barn in Somerset

Mixing engine Oils

Post by Smartbear » Mon Apr 17, 2017 5:33 pm

benv6 wrote: Mon Apr 17, 2017 2:52 pm
ronk wrote: Mon Apr 17, 2017 2:30 pm Why do you want to go 5w Ben?
I want to see what would be the MPG difference, I heard you would get better MPG with 5w40 :)
If that's your reason then you're going the wrong way, the 0w30 is a less viscous oil inducing less drag on the engine :thumbsup:
I would be surprised if you measured much difference though :?
Rob
Last edited by Smartbear on Mon Apr 17, 2017 7:01 pm, edited 1 time in total.
Image

e89 Sdrive 20i, plenty of mumbo & good economy-the thinking bears z4
e89 Sdrive 30i, this ones busted, pass me another...
e85 3.0si sold

User avatar
mr wilks
Legend
Legend
Posts: 21894
Joined: Wed Jul 04, 2012 10:02 pm
Location: Lancashire

Mixing engine Oils

Post by mr wilks » Mon Apr 17, 2017 6:25 pm

Agree with Rob , , you are more likely to see a worsening of MPG going 5w40 & a twin turbo engine where oil is a real factor in keeping running temps down i would be spending more time choosing the right oil than deciding what grades :?
5w 30 will see you right , as for which brand ?
Do some digging & some reading but in my mind Millers is the one for both cold start & hot running cycles
3 ZMRs
3 E89s
5 Si coupes
5 Si roadsters
997 C4
TTRS
F82 M4
MK7 Golf Gti
current Bmw 6 Gran Turismo

User avatar
buzyg
Legend
Legend
Posts: 26423
Joined: Fri May 20, 2011 6:11 pm
Location: Cornwall

Mixing engine Oils

Post by buzyg » Mon Apr 17, 2017 6:33 pm

Smartbear wrote: Mon Apr 17, 2017 5:33 pm
benv6 wrote: Mon Apr 17, 2017 2:52 pm
ronk wrote: Mon Apr 17, 2017 2:30 pm Why do you want to go 5w Ben?
I want to see what would be the MPG difference, I heard you would get better MPG with 5w40 :)
If that's your reason then you're going the wrong way, the 0w30 is a less viscous oil inducing less drag on the engine :thumbsup:
I would be nice surprised if you measured much difference though :?
Rob
Agree with Rob here, don't follow the logic. Interested to know the result though.
Image

User avatar
ronk
Lifer
Lifer
Posts: 14199
Joined: Tue Feb 24, 2009 11:50 am
Location: Durham

Mixing engine Oils

Post by ronk » Mon Apr 17, 2017 9:40 pm

Stick with the viscosity specified is the best advice and I would not mix oils unless absolutely necessary.

I won't mix screenwash!
You don't stop playing when you get old - You get old when you stop playing!
So I bought a 35is with all the toys to play with. :thumbsup:

User avatar
RJS-Z4
Senior Member
Senior Member
Posts: 2387
Joined: Wed Feb 29, 2012 3:43 pm
Location: SE London/Kent

Mixing engine Oils

Post by RJS-Z4 » Tue Apr 18, 2017 1:31 pm

As these chaps quite correctly say, don't mix them. Properly cheap skate thing to do...

Also, better MPG, you're going the wrong way in viscosity as is already said.

Finally, the only reason I've ever heard of people going thicker is to reduce any very slight misting/leaks that are showing on seals due to thin oil.
Titanium Silver E85 Mods Done - 224's, Stubby, Amarone //M seats, ZHP, Retrofitted Wind Deflector, Aux In

Image

User avatar
Smartbear
Lifer
Lifer
Posts: 13685
Joined: Wed Feb 05, 2014 6:54 pm
Location: a barn in Somerset

Mixing engine Oils

Post by Smartbear » Tue Apr 18, 2017 2:32 pm

RJS-Z4 wrote: Tue Apr 18, 2017 1:31 pm As these chaps quite correctly say, don't mix them. Properly cheap skate thing to do...

Also, better MPG, you're going the wrong way in viscosity as is already said.

Finally, the only reason I've ever heard of people going thicker is to reduce any very slight misting/leaks that are showing on seals due to thin oil.
I've heard of oil burning problems being diminished by using thicker oil as well :thumbsup:
Rob
Image

e89 Sdrive 20i, plenty of mumbo & good economy-the thinking bears z4
e89 Sdrive 30i, this ones busted, pass me another...
e85 3.0si sold

User avatar
benv6
Member
Member
Posts: 418
Joined: Thu Apr 30, 2015 2:28 pm
Location: Berkshire

Mixing engine Oils

Post by benv6 » Tue Apr 18, 2017 4:12 pm

:thumbsup: thanks Guys - Got my answer now :)
Now: BMW 335D Touring
Previous: 435D Coupe, BMW Z4 E89 35i, BMW Z4 E85 2.0, BMW E46 330CI

ImageImage

Post Reply