It could be ok, but it's naturally aspirated so expect a slug pulling the weight of the suburban. Fortunately it has a couple things going for it, it's old enough that it doesn't have the problematic electronic pump components and drive-by-wire present after 1993 and the transmissions are pretty hearty. I hope it has the OD trans though, that'll help with the mpg.

I can achieve 25mpg in my K1500 4x4 truck with a 6.5TD on the highway using winter blend, summer blend I don' t know, haven't exhausted my winter fuel yet.

I would probably only get it if you seriously need it, I kind of regret having gotten my truck although I do use it some, but it sits a lot. Make sure the cooling system is up to par, these (including the later 6.5) need to have optimal functioning cooling systems and good fan clutches. These can also be a can of worms too, so be prepared. The 6.2 / 6.5 (basically the same) were developed jointly with Detroit Diesel so that says something, but they still are old IDI engines...better than the problematic 5.7 Olds engine though.

my .02

Steve A

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Steve A
92 W140 OM603
97 VW Jetta TDI
90 Passat variant TDI 6 speed MT
94 Chevy K1500 6.5TD
05 E320 CDI
+ others