I just did the 5000 miles oil change. Couple days after I did a trip from GreenBay WI to Lacrosse WI, then Lacrosse WI to Minneapolis MN, back to Lacrosse, then to GreenBay. I notice there is a drop of Gas Milage. I use cruise control as soon as I am up on the highway.

GreenBay to Lacrosse - around 38, which I normally can do a 42 MPG (with 35 psi on my tires)
Outside temperature on that night was around 39F.
200 miles trip: around 80 miles on the highway driving around 70mph, and 120 miles of 2 lane local highway around 63mph

Lacrosse to Minneapolis, then back to lacrosse - unbelivable 35.7 MPG. I couldn't believe that. Total distance is around 300 miles The temperature showed 39F and my tired pressure was around 33psi. I was driving around 71 - 73 mph for the whole trip.

Lacrosse to GreenBay - around 40, with outside temperature around 45F. I inflated my tires alittle bit to 35 psi.

As winter is coming soon to GreenBay, i hesitate to inflate my tire pressure too high in order to optimize the traction in snowing condition

Any suggestion what I should do?

 

Hi Ian,

Certainly is alarming. I live in MPLS and I know that they are usually changing over to Oxygenated fuels for the winter season about this time. That typically leads to a reduction in overall fuel economy. That might be part of the reason.

Also - on tires - I just inflated mine to 42 PSI yesterday when it was 50 degrees out. They will drop about 4psi when the temps drop sub-zero.
All compressors will put a little moisture in the air-lines which get's transferred via the schrader valve in your valve stems into your tires. While the slight amount of moisture will not bother either the tire or the valve when above freezing, the schrader valves are known to leak if you introduce moisture laden air in the sub-freezing conditions. Living in the north has it's challenges - flat tires when -15f is one of them. I'm also curious if the moisture at sub-freezing will have any impact on the pressure sensors.
All of this adds up to why I inflated mine while still warm out.

 

Dear Ian,

I had a similar drop in FE after my first oil change, but in hindsight I think the FE drop was caused by something else - outside temperature.

I took delivery of my TCH in early September. I decided to have the dealership change out the oil at around 1500 mi (I'm used to the "old school" approach to break-in). I specified 0W-20, as the manual suggests. After some wrangling with the dealer (described in a post in another thread), they put in the 0W-20 (at least I think they did). At that point, I had driven about three tanks in the car, my average FE was around 41 mpg and my highest tank average was 42.3 mpg.

Anticipating similar or higher FE on the next tank, I was disappointed and a little upset to see my tank average begin to erode (I am now at 40.3 mpg with 75 miles to go on the tank). I drive mostly locally, as part of my law practice. Most of my trips follow the same dozen or so routes, so I kind of know where I should be on trip FE at any given point of these routes. I found I was coming in lower consistently at these "checkpoints".

As I now analyze the situation, I can only conclude that the average ambient temperature must be the key factor. My first three tanks were used in weather I would estimate to have been in the high 60s-low 70s. My current tank has been used in weather with highs in the low 50s.

 

Before my first oil change, my mileage had been getting worse and worse -- averaging 30 mpg! But I finally got it done at 6700 miles, using Mobil 1 Synthetic 5W-20. No improvement on the tank immediately afterwards, but after that, it was back up to ~34-35 mpg.

If it's actually worse after an oil change, maybe they used bad oil. There are petroleum 0W20 oils and they're bad -- you need synthetic for good performance.

 

Thanks everyone for their reply.
My dealer did my oil change with a 5W-30 oil....... does it sounds right to you?
After an oil change, does the engine/system needs a break-in period in order to return the milage to 'normal'?
ian

 

While I am sure it is not a big deal the car is not spec'ed for 5W30, the Oil filler and manual clearly state 5W20 or 0W20, I would go make the dealer swap it out, unless they told you ahead of time. Ido my own oil for years becasue I don't trust oil change places, they either put in too much or too little or use the wrong weight oil.

 

My mileage dropped as well after my last oil change. My service order ticket stated that 5W30 was used. I have brought this to the attention of the service manager and he claims that 5W20 was used but the computer software that prints the service tickets was wrong and assured me the correct oil was used. That being said, I have noticed a decline in the MPG since then but also even more so since it got cold. 24 degrees this morning and todays avg is 34.5 instead of my normal 36.5 or so. I believe as other posters has stated, that cold weather will effect your mileage. I have to believe the service manager who told me that they have used the correct oil. I wish there were a better way for them to prove that to their customers. If, in fact 5W30 is used, what are the problems?. I know the recommended oil is 5W20 and there is good reason for that to maximize economy, but what is the downside of oil that is a little thicker for adhesion?
Just curious.

 

5W20 isn't expensive so there's not much reason for him to lie. And cold weather makes a very significant drop in mileage.

 

After reviewing posts regarding to oil, I went to my dealer to ask why they put 5W30 while the manual states 0W20. The dealer said they asked Toyota already that 5W30 will perform the same as 5W20 or 0W20. I was like..........dah. If they perform the same, why the manual doesn't mention 5W30 at all.

Anyway, the dealer also points out that because 0W20 has a thinner layer, therefore there is a higher possibility of oil leakage... Anyone has comment on this statement?

Tonight they drained my oil and put in the 0W20, with an extra charge of $11 more. They didnot put in labor costs in.

I drove for 10 minutes around town, realize the engine is quieter and the milage is actually better. Outside is around 38F and i got 35MPG. I ran though 3 stop signs, 2 red lights, around 5 miles of distance.

 

I would complain to the general manager of the dealership about this extra charge. They didn't put in the oil weight specified by the factory, then the service dept charges you extra money to replace with the correct oil? That's ridiculous. If the GM doesn't refund your money, then take this to the district manager.