Hi Scotty,
I have 2007 Lexus gx470 with 210k miles. I changed both diff and transfer case fluid with mobil1 75w90 recently. After this job I saw drastic change in mpg. In range of 20-30%. What can be the issue? Here is what I checked out already: spark plugs are iridium and have 50k on them and look good, vaccum leak using throttle body cleaner spraying method, brake fluid which was more than max and I extracted extra out, brakes looks ok but rear one has more streaks/lines than front ones.
Out of ideas on what else to look. Please help.
bulletguy
Did you fill in the correct quantities?
Are any of the brakes dragging? (Verify with a temperature gun after driving).
I kept oil in warm water to make it more fluid. Then filled it till it dripped from the fill hole. Factory recommendation is same for transfer case and 85w90 for diff. Any issues here?
If Brake drags wheels will be hot correct? I don’t see that happening but I see circular groves in rear driver side rotor.
Is the mobil 1 fluid compatible with your vehicle? You’ll have to ask the manufacturer. Circular grooves are normal for wear and tear symptoms for brake rotors. As long as they aren’t too deep, it should be fine.
Well let's face it if it happened right after you change that fluid the fluid's too thick thick fluid causes more friction causes lower gas mileage
I also performed intake manifolds and valve cover gasket change couple months back. But didn’t observe mpg drop. Car feels like dragging a bit after transfer case and diff fluid changes. I used mobile 1 synthetic gear oil and not Toyota. 75w90 is what I used for both. Factory recommendation is same for transfer case and 85w90 for diff. Any issues here?
Differential gear oil and Hypoid gear oil are two different things. Differentials are supposed to be 75w85 while the transfer case is supposed to be 75w90.
Here is manufacturer recommended:
Differential
Front
Rear
1.5 qt. (1.4 L, 1.2 Imp.qt.)
3.3 qt. (3.1 L, 2.7 Imp.qt.)
Hypoid gear oil API GL-5
Above OoF (-18°C): SAE 90 or
SAE 85W-90
Below 0°F (-18°C): SAE 80W or
SAE 80W-90
Transfer case
1.5 qt. (1.4 L, 1.2 Imp.qt.)
Hypoid gear oil API GL-5
SAE 75W-90
Where did you get these figures from? Your owner’s manual?
Yes. Owners manual came with car.
Your information is wrong. See page 429 of your owner's manual for correct weight, grade and type of lubricants as are correctly reproduced above by @itwt.
Sorry my bad. My car model is 2007 and manual says hypoid for both.
I can’t figure outhow to edit post after sent.
I’m surprised that oil recommendation is deferent fit 2007 and 2009 when they are same generation cars
2009
https://www.manualslib.com/manual/1421933/Lexus-Gx-470-2009.html?page=429#manual
Interesting, contact mobil 1 and check if their fluid is compatible with your vehicle.
Had a chat with mobile 1 customer care. Fluid I used is recommended for my car.
Your owner's manual clearly states that Hypoid is only for the transfer case, not the differential. This article may help -
https://kendallmotoroil.com/automotive-guide/hypoid-gear-oil-what-it-is-and-when-to-use-it/
@doc Thanks for your replies.
Here is link to my car's user manual online. https://www.carmanualsonline.info/lexus-gx470-2007-instrument-cluster-lexus-2007-gx470-owner-s-manual-om60c64u/?srch=Hypoid
It states hypoid gear oil API gl-5 85w-90 for differentials and 75w90 for transfer case.
Will it be an issue if I use 75w instead of 85w in differentials? I believe no.
Specifications for oil is different for 2007 and 2009 car. I clarified that in previous post.
I don't know what owners manual you are using but it has been reproduced here for you. It clearly says the transfer case use hypoid, the differential does NOT. You apparently feel you know better than the manufacturer so use whatever you want. We have to move on to people that want help, not an argument.
Sorry @doc if you felt offended. I did not mean to. Appreciate all your help in resolving my issue.
I wouldn't be here if I knew better than manufacturer. Just tryin to find a cause and solution to my car's problem. 😐
I do not feel offended, just worn out. The issue was answered and resolved yesterday.