mpg run!!

[william]

Went on an mpg run today about 60 miles.
Here's my cars specks b6d engine e series 4 speed.
185-60-14 tires inflated to 40 psi
Round bar roof rack windows down.
Results for today were 47.4.
Used same pump and fill they same way till it was about to over flow.
I'm trying to get a base for this car to see how a grill block and front air dam will affect my mpgs.
Question is why when I drive for mpgs slow and easy on the throttle I get a code 15 ( o2 malfunction) my timing is set at 11° one over stock and I have a new o2 denso unit.
I run 86 octane quality fuel. What's the problem the light goes right out if I floor it than let up. I don't know what's going on any thoughts? ?
Also new plugs ,wire ,rotor, cap and fuel filter.

[TominMO]

I get the same thing occasionally on Matthew. But it goes away for me too, so there's no real issue. I can only guess that at minimum throttle the O2 sensor isn't seeing as much O2 as it would like. On Matthew I think it might be due to the header. But it only happens at minimum throttle, and rarely, so I'm not concerned about it.

60 miles is a very short run. I got criticized for 85 miles, altho I did get consistent results. My B6 SOHC gets 41.9 @ 60 MPH, for example, on two different runs of 85 miles. But that may be too low, due to an issue with the #1 exhaust valve. Matthew got 48 on a 250-mile drive @ 60. What speed were you using?

[william]

I was never over 50 I was just seeing what I could pull out if the b6d. Been testing 55 for several months with no mods for arodanamics 118 miles a day to and from work but I screw up a Time or 2 threw the week and the test is always messed up.
I average a solid 38. I'm trying to test the effects of my roof rack.
I seen a metro forum were a guy was getting a 7 mpg hit with his cross bar rack. I thought that was crazy high so far I have seen a drop in 1 mpg average in the past 2 weeks but the weather has been changing and messing with me lol