"I just did a full PM service (oil and filters) on my rig. Now, as soon as I hit a grade with a load, the truck feels like it’s gutless and losing boost. It was pulling fine before the service. Did the shop mess something up, or is it just a coincidence?"  Mechanic's Expert Answer: "If the power loss started immediately after a service, you aren't looking at an engine failure—you're looking at a fuel restriction or an air leak." When you change the oil, you usually change the fuel filters too. Modern high-pressure fuel systems are incredibly sensitive. Even a tiny air leak or a pinched O-ring can cause the engine to 'starve' under load, even if it idles perfectly in the parking lot. Check these 3 things before you head back to the shop: - The "Double Gasket" Blunder: Sometimes the old rubber gasket sticks to the filter housing. If the new filter was spun on top of the old gasket, it will suck air into the system. Under a heavy pull, that air bubble expands and cuts your power. - Loose Fuel Lines: If the technician bumped a fuel line or didn't tighten the secondary filter enough, the pump will draw air instead of fuel. Look for 'wet' spots around your filter housings. - The Priming Pump: Make sure the manual priming pump handle (if equipped) is screwed down tight. If it's left loose, it can act like a straw drawing air into the fuel rail. The Bottom Line: A $30 fuel filter that wasn't seated correctly can make an 600HP engine feel like a lawnmower. Don't let a shop sell you a new turbo until you've verified the fuel pressure. Pro Tip: Check your boost gauge while climbing. If the boost is lower than usual, but the engine sounds normal, you might have a loose 'Boot' on the Charge Air Cooler (CAC) that was bumped during the oil change. A simple loose clamp can cause a massive power loss.