I've been struggling with this question for several years now, having no fewer than four different oils in use with my OPE. My local conditions here in SE Pennsylvania might range from 0 degrees in winter to 100 degrees in summer. Only one machine in the fleet, that being the generator, would ever be called upon to operate across that entire range. I've decided to leave the snow blower out of this, as that is a really special purpose application very different from the others. Other than the generator, that limits the operating conditions to about 25 F to 90 F. Above 90 F I will happily wait for cooler weather.
Given my circumstances, I could just go with a synthetic 5w30 but favor something in an Xw40. There is both 5w40 and 15w40 in the fleet now. Aside from the lawn tractor, it is all pull start. The only machine running 15w40 is the leaf vacuum, mainly because it uses a lot of oil. It started a lot easier in the cooler late fall temperatures with 5w40 than the current 15w40 fill. I am never going back to the straight SAE 30 it calls for as it is very difficult to pull start it in cool fall temperatures when it is needed most.
So with that as the background, here are some of the contenders and my thoughts were needed:
1. Mobil 1 0w40. 3.6 HTHS; 12.9 KV100. This one is on the list because I have about 6 quarts on hand.
2. Mobil 1 5w40 Turbo Diesel Truck. 3.8 HTHS; 14.5 KV100. Seems to be be a happy place on that specification.
3. Rotella T6 5w40. Unknown HTHS; but 14.2 KV100 slightly less than M1 TDT. HTHS might be similar.
4. Delo 4000 XSP 5w40. 4.2 HTHS and 15.4 KV100. This one worries me for the Honds GCV160 powered equipment, particularly the push mower that is used for trimming what the lawn tractor cannot reach. That machine sees 5-10 minutes of run time per week, some of that in short start stop cycles.
Okay, so there you have it. Your thoughts: stick with a 5w30 or chose one of these or another 5w40?