I have a 2004 chevy s10 4x4 zr5 and it seems like my gas mileage has gone done this winter. I have about 150 lbs in the back for weight. is that the reason? also sometimes it feels like my 4 wheel drive is on when i am still in 2 wheel drive

Most towing advise works to the 85% rule. As long as the maximum weight to be towed is 'Not' greater than 85% of the vehicles maximum 'kerb' weight, (maximum gross weight).
The Musa should not pull over 1000kg, (1 metric tonne). A braked trailer will allow that weight to rise by about 200kg.

two thirds of the weight of the towing vehicle ,so if you look at the paperwork of the car for unladen vehicle weight then two thirds of that ,europeon legislation

what oil did you use? generally 5w30 is standard, but you can use other oil weights depending on environment, i.e. 10w30. the numbers correspond to the viscosity of the oil. heavier weight oil such as 10w30 is better in the hot summer months, where 5w30 should be used in cold winter months

How old is battery and clean connection.Could have 12.5V but do not havecrank power.

Replace air filter.

Most likely 5W-30. The W is for winter. The numbers tell summer and winter. A quart of this oil will act like 5 weight (very thin) in the winter and 30 weight in the summer (thicker). Let's not go in to how that is done.
If you live up north, a 5W-20 would do well also. Down south 10W-30 is often used.

sounds like a restriction in the exhaust possibly catalytic converter...........

Talk to your local tire store an dsee what they recommend. I'm sure they will know what to do.

Generally gasoline is reformulated in the fall until mid-winter and it is not uncommon to notice a significant drop in mileage. If the vehicle has been maintained and has not had a problem recently, and is not displaying other symptoms - like smoking or performance problems - the best thing to do is wait till spring and see if it picks up again. You may even notice a placard on gas pumps saying gas is reformulated during winter months.

Directly from the Toyota Spec Book:

Maximum trailer weight: 1,500 lbs
Maximum tongue weight: 150 lbs

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