I've been running propane on my Blazer for the last 7 years or so, here's my take:
1) propane is very expensive here compared to gas.
It varies, just like any fuel. When I converted, it was about 2/3's the cost of gas. It is a bit more than gas now.
2) you have to wrestle a 100 lb forklift tank on and off the truck every time you want to fill it up because most places won't refill while it's on/ near a vehicle.
Yep, taking the tanks in/out sucks. They're less than 100# but still not fun. And in a lot of places they aren't legal inside an enclosed cab.
3) it works bad when it's cold, at least until the truck warms up, because it needs heat from the antifreeze to evaporate the propane from gas to vapor before the carb.
This one is not right at all.
Propane boils at -44*F, gasoline boils at more than 100*F (actually as high as 400*F, the actual number varies depending on what is actually in the gasoline).
The reason that gasoline engines have trouble starting in cold weather is because the fuel can only burn as a vapor. When cold, the engine was pumping air and liquid fuel and those don't burn. The 1st solution was to "choke" the engine and run tons of extra fuel, that way enough of the liquid fuel vaporized to get the engine started.
Even below the boiling point, some of the liquid will boil; just like if you leave a pot of water out for a week it will eventually disappear even if the temperature was never over 212*F. Same thing with steam over a hot tub, lots of water "boiling" (vaporizing) without the whole amount of water making it to boiling temp.
Propane doesn't have this problem at all, because it boils at such a low temperature, it's basically a vapor at any temperature we would use them at. The reason that coolant lines are run to the vaporizers are to keep them from freezing up; as the liquid propane converts to vapor it takes heat with it (just like pretty much anything does).
If there isn't warm coolant running to the vaporizer, under high fuel requirements they would get too cold and stop delivering vaporized fuel and it would stay liquid. No bueno, basically you can't expect full HP out of a propane engine until the coolant is up to temp. But you really should let pretty much any engine get up to temp before full throttle anyway.
4) propane makes less power than gas (less heat content) in a given engine. It is a higher octane so you could run an 11:1 compression if you want to rebuild.
100% true on paper. But Cary @ GotPropane makes a good point that many don't lose power because the carburetors they're replacing weren't tuned right and the new propane system, which pretty much runs perfect out of the box (vapor fuel is magical that way, liquid fuel is the reason carburetors are so finincky). I didn't notice any loss of power going from gas to propane.
5) a TBI system is just as cheap, if not cheaper. You can get used computers and harness for a couple hundred bucks. Or get one of the new systems out there.
Agree 100%. Propane isn't the answer for everyone. Honestly, the only reason I did it is because I thought my cam was too big for TBI and the fuel injection systems then were $$$ (gen 3 stuff was brand new then). And I got a smoking deal on a new system in the "for sale" section here.
6) you're very limited on where you can refill a propane tank.
This is my #1 overall complaint with propane. Filling the tanks sucks. You have to take them out yourself (not so bad) but you also have to find a place that has propane (about 1/5 of gas stations, in my experience) AND hit them up at a time that someone "certified" is available to fill them.
You can't fill the tanks yourself.
The most frustrating experience for me was at Blazer Bash a few years ago, our campsite had a propane fill station (very common at KOA type places because RV's use a lot of propane). I stopped in after our trail ride one day at 4PM or so assuming someone should be there to fill my tanks (already knowing that filling propane can be troublesome). Nope, the only employee they have certified to fill tanks took the week off.
After all of that, I very recently had a chance to bail on propane and I didn't. My 383 finally let go at the beginning of June and I decided to replace it with a 6.0L (I decided that building a Gen I small block that would take the boost I'm running would be a lot more $$ than a stock Gen III that would take it stock).
The Gen III fuel injection system is excellent, but I would've needed a fuel cell, fuel pump, new fuel system etc. and that's a bunch of extra cost. And, with a turbo, would've required a full day on the dyno (again, propane is magic there, as a vapor fuel you can make the air/fuel work right with pretty much no adjustments).
Long story short for propane:
Pros:
#1 It's ridiculously simple. Like, makes carbureted engines look complex. No fuel pump, no jets to mess with, runs at any angle. One wire to run it (or none if you use a vacuum lockoff). It straight works and it works really well. I've been on the trail with a bunch of fuel injected vehicles that wouldn't run with a bad fuel pump, MAF, IAC etc and felt pretty good knowing that I don't even need those parts.
Don't get me wrong, everything can break and go wrong, but even if the lockoff goes bad (the part that says start/stop in a propane system), you can bypass it and let the engine start/stop with the valve on the tank like a barbeque grill.
High octane fuel, 97-110 (quality seems to vary but even 97 is pretty good). Part of the reason I kept it and part of the reason mine is boosted now.
Cons:
Refilling tanks SUCKS. Physical labor aside, it's a pain to find a place to fill them. And it takes a lot longer, because you can't fill them yourself. And you need to think ahead, you're not going to get propane at midnight anywhere.
I stuck with propane because of simplicity and because it likes boost. And mine's a trailer queen that only goes through a couple dozen tanks of fuel a year. But it's not for everyone.
