How-To GuideBeginner

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

Step-by-step oil and filter change procedure for passenger vehicles, generators, and small engines. Intervals, oil selection, disposal, and the mistakes that cost engines.

Salt & Prepper TeamMarch 30, 20268 min read

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

MistakeConsequencePrevention
Not checking oil level between changesEngine runs low, damage occursCheck monthly
Over-tightening drain plugStripped threads in oil pan ($300+ repair)Snug, not torqued
Forgetting to install new filter gasket lubricationFilter leaks or sticksAlways wet the gasket
Adding too much oilFoaming, seal damageAdd conservatively, check dipstick
Using wrong viscosityIncreased wear, poor cold startsCheck the manual
Running new generator without break-in oil changeContaminated oil throughout the engineChange at 8 hours

Sources

  1. API — Motor Oil Guide
  2. Briggs & Stratton — Oil Recommendations

Frequently Asked Questions

How often do I actually need to change my oil?

Modern full-synthetic oils in modern engines: every 7,500-10,000 miles or once per year is typical. Conventional oil: every 5,000-7,500 miles. The old 3,000-mile interval was for older engines and older oil formulations — it's largely obsolete for post-2000 vehicles. Check your owner's manual for the manufacturer's interval; synthetic-capable engines specify longer intervals.

What happens if you run an engine low on oil?

Oil provides a lubricating film between metal surfaces. When oil is critically low, metal contacts metal, friction heat builds rapidly, and the engine seizes — sometimes catastrophically. Connecting rods break, crankshafts score, bearings weld. The repair cost is typically total engine replacement. A $30 oil change prevents this. Check oil level monthly.

Can I mix synthetic and conventional oil in an emergency?

Yes. Mixing synthetic and conventional oil of the same viscosity rating is safe for short-term use. The performance will be between the two, not compromised. In an emergency, adding a quart of the wrong type or viscosity is far better than running low. At the next opportunity, drain and refill with the correct specification.