Sudden Drop in MPG after last service! Advise & Suggestions needed.

[allyghee]

Hi folks,
Due to my location, my last service with a Toyota dealer could not come on so I did a quick oil change a fuel station. This is what was done.

1. Engine oil change.
2. Both oil in the front and back axle were topped up.
3. Did not change engine oil filter as it wasn't available for purchase at the location
4. Swapped my AC filter with a spare I had.
5. Wheels balancing and alignment.

After this my MPG has dropped significantly from 17.somthing to 14.1

I will like to know why. Also my Toyota dealer advised I do not use synthetic engine oil. His main reason is that it lengthens the duration between servicing. Question is, can I still move to synthetic and still maintain standard oil changes as organic oil? I used the oil below, is it a good one for us in Ghana where it'd mostly hot and our coldest weather is about 19°Celsius.
Thanks in advance.

 

[MikeInNH]

Is 15w-40 the normal weight oil you use...or just this time?

I think 15w is too thick. Use a 10w-40, or even 5w-40.

You can switch to full synthetic oil and back or mix them any way you want.

Question is, can I still move to synthetic and still maintain standard oil changes as organic oil?

Not only YES....but you should. Don't change the interval.

Everything you're asking is in your owners manual. Have you read it?

 

[fullboogie]

How do you know your mileage has dropped? If you're going by the dash indicator, it's probably wrong. Every time I take the battery cable off my engine (and everything resets),j it takes a tank or two for the mileage indicator to normalize. Until then, it's whacky and way off (more so than usual, I should say).

I'm betting the dealer disconnected your battery.

 

[hullinger]

I wonder if the MAF is getting cruddy or an O2 sensor took a crap. I don't know a whole lot about these sensors but I believe that when the computer can't get a good reading it reverts to a basic air/fuel ratio setting which results in a drop in MPG.

 

[V8Limited4wd]

I'm guessing it's the 15W-40 that caused the drop in MPG. Stick to lighter weight oil and don't listen to the dealer's nonsense about not using synthetic. Synthetic oil is better for the engine and you can have a longer oil change interval.

 

[emoore924]

That's a big move. If anything, it is probably the result of a combination of a couple of things.

The weight of the oil will matter a little. Heavier oils will adversely impact MPG a little. Here in the US I believe the FSM recommends we run a 5w30 in most weather conditions.

Synthetic oil will be a little more efficient than "dino" oil.

Not sure what they put into the differentials but the same story exists there -- higher viscosity non-synth oil will slightly impact the efficiency of the vehicle.

The computer may have been completely reset.

If you want to know what your MPGs really are, fill your tank. Reset the trip odometer to zero. Reset your computer to zero. Drive for a while (use more than 1/2 a tank). Fill your tank again. Take the # of miles on the trip odo and divide that by the # of gallons you just put into the car -- that's your actual MPG. Compare with your computer reading. There ya go.

 

[earthrealm]

you need to confirm how you noticed the mpg, also confirm if the dealer disconnected the bttery terminals, you would know this by your rear wiper needing a reset or your trip meter reading zero

 

[allyghee]

Thanks guys for the tips. Very much appreciated.

Based on your expert advice;

1. I am definitely moving to synthetic for my engine oil.

2. I will also need some advise on the type of differential oil to use. I will like to start anew.

3. I am changing my transmission fluid on my next service.

Thanks

 

[Oneluv13T4R]

Whenever you get an alignment done afterwards your suppose to do zero calibration on your 4Runner ...that's is thee answer to your loss of mpg. Nothing else

 

[Oneluv13T4R]

Thanks guys for the tips. Very much appreciated.

Based on your expert advice;

1. I am definitely moving to synthetic for my engine oil.

2. I will also need some advise on the type of differential oil to use. I will like to start anew.

3. I am changing my transmission fluid on my next service.

Thanks

1 Mobil 1 synthetic 5w-30 or Amsoil synthetic

2 75w-90 Mobil 1 or Amsoil

3 Toyota ATF -IV or ATF-WS

GOOD LUCK and enjoy the feeling of fresh fluids