I find a fair bit of variation with mine, but I know that one factor is where I fill up. One place is on a slope and depending which side you are on make a difference in your fill and then another place where I fill it is level, but I have to be careful in filling because it is a pump with to nozzle sizes and a pump fill rate that is very, very fast (it is for trucks).

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Current:
1985 300D aka Miss Margaret
1991 300SE aka Alarice
1995 SL320 aka Samantha
1997 K1500 Silverado
Past:
1999 E300 ex-wife got it and let her son ruin it
1984 190 2.3 ex-wife got it and let her son destroy a great car
1985 300D (CA version) aka Maybelline lost to deer at high speed.
1981 300D aka Madeline (went to salvage at near 400k) rusty, yet best car I ever drove
Wishlist:
McFarlan TV6 (only a few privately owned)
ReVere with Rochester engine
1917 Premier (only one left)