I have the best of BOTH worlds....a 150 diesel. Over the years, I've bought and re-sold dozens of 135's and 150's. They are extremely popular tractors in this immediate area. (Greatest MF dealer on earth just a few miles down the road among other reasons)
OK...MF135's vs MF150's (w/o considering engine type)
The 135 is a great little tractor. Compact in size, big on performance. Good power to weight ratio, excellent 3-point hitch design and draft control, parts availability galore, and a re-sale value unmatched.
The 150 is all that AND better balance, better chassis to mount a loader, more cooling and fuel capacity, better air filtration, and most all the features that are options on a 135 are standard equipment on a 150.
Gas vs diesel.
You have two possibles on the gas engine. Very early and very late production 100 series were offered with the Continental 4-cylinder. Some of the initial crop of 135's had Continental Z134 (134 cu in) but MOST were Z145's. BOTH were rated @ 38 hp. For the lions share of the production run, they were equipped with the Perkins AG3-152 3-cylinder gasser. It shares a multitude of common parts with the diesel version. ALL are really good, solid engines. Neither has a definite advantage over the other. PERSONALLY, I like the Z145 gasser, but can't really tell you why....As far as gas engines go, they are fairly easy on fuel consumption. I don't care for gas engines of the last few years of production. They had the beginnings of emission reduction equipment on them, and can be a problem.
When you speak of 135's OR 150 diesels, you're talking the most fuel efficient, reliable engine of its day. When the MF150 diesel was initially tested at Univ of Nebraska, in 1964, it was the most fuel efficient tractor to date. It STILL ranks up there with todays tractors. (I've plowed all day, in hard alfalfa sod, and never burnt a gallon an hour on my 150) Engine rebuild kits for a Perkins AD3-152 are amongst the cheapest engine kits available. And the best part, they will outlast the Energizer Bunny! These things are incredible. The AD3-152 stayed in production for over 50 years. Not many engines are even in the same league.
OK...Pick ONE.... Tie breaker for me is the diesel. If I couldn't have a 150 diesel, it would be a 135 diesel....The engine is just that special. A diesel 150 will work circles around a diesel 135. A gas 150 still has a very slight performance advantage over a 135, but at a cost.
But....long and short of it....NEITHER would be a bad choice. And we are talking tractors that could be as much as 47 years old, to a NEWEST of 36 years old. (us built) (1964 to 1975) You're buying over-all condition of an individual used tractor. The gasser could potentially be in much better condition, or vice versa...
With EITHER, the 135 or the 150, if they're in decent shape, you won't go wrong IMHO.
