SAE 5W40 Synthetic


Asked by Jul 25, 2016 at 08:30 AM about the 2015 Subaru XV Crosstrek Base

Question type: Maintenance & Repair

The SAE 5W40 Synthetic, is it allowed that the
concerned engine could be filled with ?

This Engine Oil Type caused ;
1- High Oil Consumption than normal.
2- Tremendous Fuel Consumption.
3- Very very bad throttle response.
4- Early AT Oil Temp warning light Alert (No chance
to run 160 km/hr for more than 5 minutes -
ridiculous )

7 Answers

Bob Beaman

In my opinion putting that oil (5w40) in a Subaru you would likely not notice anything, but a very slight drop in fuel mileage and I doubt this drop would be easily measured. It would have no effect on throttle response or AT oil temperature. The recommended oil is 0w20 synthetic and some of the 2015 engines suffered from excessive oil consumption.


Sorry Bob, but this not true...The gas station visit intervals are doubled, more time to get response stepping on the Gaz, the CVT warning Light became a nightmare and a big Bain...that is normal when you use a double viscosity than design...Top of that 5w40 Synthetic is not allowed by the manual...Top of that, the Japanees mentioned this SAE as CONVENTIONAL Oil only and in case of unavailability of 0w20 and to be used for only one time to replenish the oil shortage in engine, on condition to go back to 0w20 next oil change.

Bob Beaman

You asked a question and answered it. I believe you have other issues. I am not an expert with Surbaru though. I am not understanding why you asked a question when you already know all the answers. Best of luck with it.


I thought you will provide me with more details about how much this oil (5w40 Synthetic) is destroying this Design of engines...your answer was a shock. I'm sorry and thank you.


Elshefei, your response that the 15w50 is causing these problems is COMPLETELY erroneous. Only if used below about 0F will cold start issues become evident...maybe. If you have an AT light on then I'm guessing an idiot put the engine oil in the CVT! In that case draining the CVT and refilling will probably NOT be enough to clear out the motor oil contaminating it, and a power flush would be indicated, following of course by carefully refilling with CVT fluid. Sheesh....


No Mentioning what so ever for 15w50, Please read my question again.


You can consider 15w40 and 15w50 identical for Subaru motors. Either are far better at reducing consumption at hot temperatures than the skinny 0w20 (which should be used only in winter in coldest climates).

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