I just bought a 98 Volvo 610. It has the 11:1 Detoit engine with 3:70 axels and a 9 speed transmisson. I am thrilled with this truck,I was pulling with a chev 1 ton.I was only getting 5 to 6 m.p.g. with the chev, with the Volvo I am getting 12m.p.g.pulling a 30ft. trailer, I get 14.5m.p.g. bobtailing.I no longer worry about hill or headwinds.I believe towing with a semi tractor is the best kept secret out there.