Motorhome Gas Engines
July 26, 2012
Filed under RV Tech Q&A
I am looking for an impartial opinion from neither a Ford nor a GM/ Workhorse fan. I am considering buying a used 2005 or newer motorhome and would like an honest opinion about which engine is better on both flat and mountainous terrain (Ford 6.8-L or GM 8.1-L). I don’t think the Ford has enough torque for the mountains.
Mike Mathis | Via email
Anytime we have a GM versus Ford question, we’re bound to get a lot of comments, but here it goes. High torque at low rpm is helpful for getting a heavy load moving away from a stop. With an engine, you can’t have torque without rpm, and you can’t have horsepower without torque. However, horsepower is the unit of work that can best be used for comparison for hill-climb speed capability. Horsepower (hp) is a measure of work over time: hp = torque x rpm/5252. The 2005 Ford F-Series Super Duty 30-valve SOHC V-10 is rated 362 hp at 4,750 rpm and 457 lb-ft of torque at 3,250 rpm. The 2005 Vortec 8100 V-8 16-valve pushrod engine is rated 330 hp at 4,200 rpm and 450 lb-ft of torque at 3,200 rpm.
Both engines are fairly close in specs, but the Ford’s three-valve-per-cylinder SOHC design is a little more rev happy, while the pushrod two-valve-per-cylinder Vortec reaches its peaks at lower rpm. Assuming that two engines are pulling the exact same loads, and their gearing is ideal for the task, the engine with more true hp (not brochure hp) will get you up the mountain faster. But in real-world comparisons, the engines don’t always have gearing perfect for operating conditions, and there are other factors like fuel mileage, engine sound in the cab and engine feel to the driver. Therefore, I suggest you test drive motorhomes with both engines and decide for yourself which one you prefer.
— Ken Freund