Ah Oil. Can't live with it, can't live without it.
Despite the recommendations for 5W-30 in all applications by the manufacturer in this case, I think a few considerations should be made.
- "Cold" Startup: is it -20 or 90F
- 5W-30 has the same viscosity whether synthetic or dino
- Just speculating, but wouldn't the manufacturer reccommend the most efficient oil to meet CAFE standards?
- Modern cars have many oil-pressure-based operations
First, I'd be more comfortable with a
slightly heavier oil in extreme heat, and if operating under the "severe" maintenance schedule's conditions (maybe like a 10W-40).
Next, I have to throw-in that for viscosity's sake, 5W-30 Syn and Dino have the same "thickness", right?
Last, on a Honda with i-VTEC, you have a variety of critical engine components that run on oil pressure -- one of which is the variable valve lift actuator. If I had to guess, the cam timing adjuster probably runs on pressure as well. I wouldn't feel comfortable messing with the recommendation of Honda to run 5w-30 24/7/365.
For older, or less-complex engines (without VVT, etc.), perhaps 3 independent, monitored, double-blind experiments with a variety of oil weights and types will settle the arguement. I don't trust "testimonials" or manufacture-sponsored experiments unless independently monitored, and easily reproduced. Until then, as Matt said, a blanket statement for all cars and engines is useless, as we've learned.
RH77