These threads remind me of how I used to be; really worried with warming up an engine and not lugging it. As a kid, I would tell my dad not to lug up that hill in 4th, he'd ask me why and I'd imagine the pistons scuffing up against the wall and cringe. I always
always started the cars as early as I could when we were going out. My mom would get mad and shut it off for like 30 seconds, then start back up immediately and drive off. But back then, I had no concerns about running 10w40 SG oil in the dead of winter for a car that just drove up the road twice a day to pick up my sister from work, no no, it was about warm up and letting the oil flow. Note: 10w40 + 1 minute drive each way for years, and that engine was still ran great when the fella we sold it to scrapped it.
As I aged, so did my rationale.
Don't be fooled by engine shuddering. It's not how you determine engine strain, or lubrication quality, or wear level. Just because you can feel the engine "shudder" doesn't mean suddenly there are all these massive accelerative forces on the bearings and pins, it just means that the engine's no longer damped internally (via combustion pressures interacting with flywheel mass and engine mass) and now transfers low-frequency harmonics to the mounts. Conversely, just because your balance-shaft fitted undersquare 4 cylinder "feels" smooth at 7K RPM doesn't mean the the reciprocating assembly
isn't violently changing directions 233 times each second and accelerating to 4500fpm.
That said though, not all engines shudder at low RPMs. I can pull off from 500rpm quickly and smoothly in 2nd without the engine shaking or combustion becoming unstable (no knocking, clacking). On 4 cylinders, they're just inherently unable to damp their own resonances at 500rpm, but I'll still smooth-engage the clutch at 1K rpm and acceleration right off that, and not worry about it, even with 48mm rod journals and 5w20 re-refined oil in the 1.8L 4 cyl. The pistons in any of my engines don't slap either when cold or lugged. The Camry used to and the GM LX9 rattles a when cold, unloaded- the cringe factor alone will keep you off the throttle in those things.
Some 4 cylinder diesel engines reach their 95% peak torque at 1200rpm and carry it to like 3500. Big whoop.
Originally Posted By: Falken
So, end of story, don't lug an engine. The bearings take a beating and everything else.
Aside from sitting in a parking lot in neutral and revving the snot out of a car like a kid, lugging an engine is THE worst thing you can do that involves lack of driver experience.
No surprise there! While a HD diesel engine can easily chew itself up, most of our engines cant possibly be able to produce the torque and heat that a HD diesel engine can, at an RPM low enough to do any damage. If so, countless V8s and now eagerly upshifting eco-4/6cylinders would be eating themselves alive cruising on the highway and lugging around in the city with their sub-1500rpm acceleration, especially with that water-thin 0w20
Of course, full throttle at 1400rpm is not ideal, I would prefer 70% throttle at 1400rpm; keep the sequential injector pulses down (hard-limiting fuel consumption), keep the fuel trim not overly enriched (dynamically limiting fuel consumption). So I guess it's combustion stability that's my main concern about lugging, and not mechanical integrity; at least not on my aspirated gasoline engines.
