So I have a 2002 L4310 with 620 hours on it. It’s used for flail mowing. The tractor would always let out a quick puff of dark smoke upon startup. No problem. Now it’s letting out a puff of smoke when I stab the throttle pedal or quickly increase the hand throttle. The smoke might have hints of white or blue in it, hard to say. All pretty minor and tractor runs fine. I just changed the engine oil and filter, no change in the smoke condition. Antifreeze smells clean. Oil that came out looked normal. Air cleaner appears clean. This tractor runs at full throttle much of the time mowing, and I did start fueling it from diesel in the transfer tank in my pickup. But it’s filtered and same brand diesel I always ran. I want to be sure I’m not facing some looming mechanical problem. Thoughts?