A few weeks ago I managed to get 44 mpg with a cetane additive on a highway road trip on a cold, windy day. Speeds ranged from 35 mph in the snow drifts to 70 mph on the open freeway (2003 VW GLS wagon, automatic).
Since then a loose tie rod was replaced and the front end straightened so the drift to the right was corrected. I also had the two tires with the slow leaks seated and sealed properly.
I was expecting a slight improvement with these changes, but on this last road trip, the mileage dropped to 34 mpg. It was another windy day with some snow drifts and icy patches, but nothing as bad as the prior trip. The return trip over the same route on a wide open road yielded a little better 36 mpg.
Fuel, terrain, driving behavior, load, etc. were essentially the same coming and going.
The first few road trips I was getting 39-41 without the additive.
There isn't a fuel leak, so what could cause such a dramatic change?
Since then a loose tie rod was replaced and the front end straightened so the drift to the right was corrected. I also had the two tires with the slow leaks seated and sealed properly.
I was expecting a slight improvement with these changes, but on this last road trip, the mileage dropped to 34 mpg. It was another windy day with some snow drifts and icy patches, but nothing as bad as the prior trip. The return trip over the same route on a wide open road yielded a little better 36 mpg.
Fuel, terrain, driving behavior, load, etc. were essentially the same coming and going.
The first few road trips I was getting 39-41 without the additive.
There isn't a fuel leak, so what could cause such a dramatic change?
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