Oil and Filter Change: Cars, Generators, and Small Engines

Tools and Supplies

For a passenger vehicle:

• Drain pan (minimum 5 quart capacity)
• Socket set with oil drain plug size (typically 14-17mm)
• Oil filter wrench (band type or cap type matching your filter)
• New oil filter (match by vehicle year/make/model)
• New engine oil (correct viscosity and quantity — check owner's manual)
• Funnel
• Rags or paper towels
• Gloves

For a generator or small engine:

• Drain pan
• Appropriate wrench for drain plug
• New oil (correct specification per engine manual)
• Note: most small engines do not have oil filters; larger generator engines may

Passenger Vehicle Oil Change

Step 1: Preparation

Warm the engine for 3-5 minutes before draining — warm oil flows faster and carries contaminants out more completely. Do not change oil on a cold engine that hasn't run recently; the oil will be thick and leave more contamination behind.

Park on a level surface. Engage the parking brake.

Step 2: Access and Position

Step 3: Verify and Record

Check the drain plug and filter for leaks after the first drive. Note the mileage and date on a sticker inside the door jamb or in a vehicle log.

Generator Oil Change

Generators require oil changes more frequently than vehicles by hours of use. A generator running for an extended outage accumulates hours quickly.

Identifying the Drain Point

Small generator designs vary. Most have one of:

• Drain plug: A threaded bolt on the bottom of the crankcase (same as a vehicle, smaller scale)
• Drain tube: A flexible hose capped with a plug, routed to a convenient drain point
• Tipping method: Some small generators are designed to be tipped onto their side to drain; the owner's manual specifies the correct direction (wrong direction can flood the carburetor with oil)

Consult your generator's manual before the first oil change — the procedure varies.

Intervals

• New generator break-in: Change oil after the first 8 hours of operation. Metal particles from the new engine shed during break-in need to be removed.
• Ongoing: Every 100 hours of use or annually, whichever comes first
• After extended hard use (running at high load for many hours continuously): change earlier

Oil Specification

Most small 4-stroke generator engines specify SAE 30 for temperatures above 40°F, or 10W-30 for variable temperatures. Check the specific manual. Using the wrong viscosity causes increased wear or inadequate cold-weather starting.

Small Engine Oil Change (Mowers, Tillers, Pumps)

Most single-cylinder walk-behind mowers and similar equipment use the same principles:

• Drain plug or tipping method — same as generator
• Oil specification: SAE 30 for warm weather; 10W-30 for variable temperatures; synthetic 5W-30 acceptable in most modern small engines
• Quantity: Most small engines take .6-1.5 quarts
• Interval: Once per season (spring is the traditional time) or every 50 hours

A useful trick for mowers without convenient drain plugs: an oil evacuation pump (hand pump or electric) draws old oil out through the dipstick tube. Takes 3 minutes and avoids dealing with drain plugs on engines close to the ground. These tools cost $10-25 at auto parts stores.

Oil Selection

Understanding the Numbers

SAE viscosity numbers (e.g., 5W-30):

• The first number (5W) is cold-weather viscosity — lower numbers flow better in cold
• The second number (30) is hot operating viscosity — higher numbers maintain film thickness at temperature
• Single-weight oils (SAE 30) are only appropriate in a narrow temperature range
• Multi-weight oils (10W-30) work across a wider temperature range

API service rating:

• The two-letter API rating (SN, SP, etc.) indicates the standard the oil meets
• Use the current rating or one generation back — SN or SP for most modern gasoline engines
• Diesel engines require different ratings (CJ-4, CK-4)

Which Oil to Buy

For a modern passenger vehicle: use the viscosity specified in the owner's manual (usually 5W-20 or 5W-30), full synthetic, from a major brand. The price difference between conventional and synthetic is $10-15 per change; the protection difference at high temperature and extended intervals is significant.

For generators and small equipment: use the viscosity in the manual (usually SAE 30 or 10W-30), conventional or synthetic. Synthetic is fine in small engines; some manufacturers specify conventional for break-in.

Oil Disposal

Used motor oil is hazardous waste. Never pour it down a drain, into the ground, or into the trash.

Disposal options:

• Auto parts stores: AutoZone, O'Reilly, Advance Auto Parts, and most others accept used motor oil free of charge. Keep it in a sealed container.
• Municipal hazardous waste collection: Most municipalities have periodic or permanent collection sites
• Service stations: Many accept used oil

Used oil in a sealed jug transported to any of these locations is the correct procedure. The oil is then recycled into re-refined base oil or burned as industrial fuel.

Common Mistakes

| Mistake | Consequence | Prevention | |---------|-------------|------------| | Not checking oil level between changes | Engine runs low, damage occurs | Check monthly | | Over-tightening drain plug | Stripped threads in oil pan ($300+ repair) | Snug, not torqued | | Forgetting to install new filter gasket lubrication | Filter leaks or sticks | Always wet the gasket | | Adding too much oil | Foaming, seal damage | Add conservatively, check dipstick | | Using wrong viscosity | Increased wear, poor cold starts | Check the manual | | Running new generator without break-in oil change | Contaminated oil throughout the engine | Change at 8 hours |