[therink]

I want to start off by saying I dont want to start a gas vs diesel debate. I am looking for input based on my own situation. I am considering on upgrading my current 3500HD SRW gasser in sig below.
My truck use: I tow my fiver maybe 2k yr (last year kept it a seasonal site and towed maybe 500 miles). My gasser with 4:10 axle does the job just fine towing my 12k fiver. My truck is a daily driver used for my business and tow equipment trailers maybe once per month. My daily commute is mostly highway and about 20 miles each way. I put on about 20k/year (mostly highway). I average about 12 mpg with gasser, and about 9 when towing. I do my own oil changes/maintenance and keep my truck in showroom condition. Since I live in salt band, I get new truck about every 3 years before the first sign of rust appears. If you drive in salt, you know what I mean.
I am considering a new 3500HD and want a Duramax, but not sure if in the long run (resale value in 3 years) if diesel is a good investment at $8500 extra. I ran the numbers and the trade vale on my current truck would be about $5 k higher if it were a Duramax.
Please dont provide opinion based on "diesels tow better" or "go diesel or go home". I want to know what you think makes sense in my situation. Thanks for the insight.