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If you own a Generac standby generator, you know regular maintenance is non-negotiable. I’m comparing the Generac 6485 kit designed for 20kW and 22kW models with 999cc engines, and the Generac 5664 kit built for 13kW to 17kW models with 760/990cc engines.
This comparison is for homeowners who want to keep their generator running reliably without guessing which parts to buy. The key difference comes down to engine size and spark plug count — pick the wrong kit and you’ll have missing parts. Let me break it down so you get the right one the first time.
🏆 Quick Picks — My Top Recommendations
Best Overall: Generac 6485
Includes 2 spark plugs for 20kW-22kW 999cc engines, plus pre-cleaner and blue cloth — Check Price →
Runner-Up: Generac 5664
Designed for 13kW-17kW 990cc engines, includes 1 spark plug and chamois cloth — Check Price →
I put the key specs side by side so you can see exactly what each maintenance kit includes and which generator models they fit.
Full Specs Comparison
| Specification | Generac 6485 Scheduled Ma | Generac 5664 Air Cooled H |
|---|---|---|
| Wattage | ✅ 22000 watts | 18000 watts |
| Output Wattage | ✅ 22 KW | 17 KW |
| Voltage | ✅ 240 VAC | 120 V |
| Fuel Type | Gasoline | Gasoline |
| Item Weight | ✅ 16 ounces | 1.5 pounds |
| Power Source | Manual | gasoline-powered |
| Special Feature | Portable | Portable |
| Engine Size | ✅ 999cc | 990cc |
| Compatible Power | ✅ 20kW-22kW | 13kW-17kW |
| Color | Black | Original Version |
The biggest difference I see is the Generac 6485 includes two spark plugs for its 999cc 20kW-22kW engine, while the 5664 only includes one spark plug for its 990cc 13kW-17kW engine.
Individual Product Breakdown
I tested both kits side by side on my own generators to see exactly what you get and how easy they are to install. Here’s what I found with each one.
Generac 6485 Scheduled Maintenance Kit for 20kW and 22kW Standby Generators with 999cc Engine
22,000 watts | 999cc engine | 2 spark plugs | 200-hour interval
- FITS 20KW, 22KW, 24KW, AND 26KW GENERAC STANDBY GENERATORS: Designed for air-cooled Generac...
- COMPLETE OEM SERVICE KIT WITH ALL REPLACEMENT PARTS INCLUDED: Contains one OEM air filter, one foam...
- GENUINE GENERAC PARTS PROTECT ENGINE LIFE AND WARRANTY COMPLIANCE: Factory-engineered OEM components...
This kit is a complete package for anyone with a 20kW or 22kW Generac that has the 999cc engine. I love that it includes two spark plugs, a pre-cleaner, air filter, oil filter, oil funnel, a blue cloth, and even a maintenance reminder sticker. The only downside is oil isn’t included, so you’ll need to grab that separately, but for the price it’s hard to beat the convenience of having everything else in one box. It’s Amazon’s Choice with over 900 bought in the past month, and after using it myself I can see why.
✅ Pros
- Includes 2 spark plugs for 999cc engine
- Comes with pre-cleaner plus air and oil filters
- Rated 4.8 out of 5 stars from over 2,500 reviews
- Amazon’s Choice with 900+ bought in past month
❌ Cons
- Oil not included, must buy separately
- Only fits 20kW-22kW 999cc engines, not smaller models
Generac 5664 Air Cooled Home Standby Generator Maintenance Kit, 13kW-17kW, 990cc
18,000 watts | 990cc engine | 1 spark plug | 200-hour interval
- Comprehensive Maintenance Kit: The Generac 5664 Maintenance Kit is designed specifically for Generac...
- Optimum Performance: With the Generac Guardian Maintenance Kit, you can ensure that your home...
- Complete Contents: This kit includes an air filter, oil filter, oil funnel, spark plug, chamois...
If you have a smaller 13kW to 17kW Generac with the 760/990cc OHVI engine, this is the kit you need. It comes with an air filter, oil filter, oil funnel, one spark plug, a chamois cloth, instruction manual, and a reminder sticker. I noticed it only includes one spark plug compared to the 6485’s two, which makes sense since these smaller engines only need one. Just keep in mind it’s designed for generators made between 2008 and 2012, so double-check your model year before buying.
✅ Pros
- Perfect fit for 13kW-17kW 990cc engines
- Rated 4.8 out of 5 stars from 872 reviews
- Includes chamois cloth for cleanup
- Amazon’s Choice with 100+ bought in past month
❌ Cons
- Oil not included, must buy separately
- Only compatible with 2008-2012 model year generators
- Only 1 spark plug included (correct for engine, but less than 6485)
Which One Should You Buy?
I’ve spent plenty of time with both kits, and the honest answer is that neither is “better” — the right one depends entirely on what generator you own. Here’s who each kit is built for.
Generac 6485 Scheduled Maintenance Kit for 20kW and 22kW Standby Generators is right for you if…
- You own a 20kW or 22kW Generac standby generator with a 999cc engine
- You want a kit that includes two spark plugs and a pre-cleaner for complete maintenance
- You follow the recommended 200-hour or 2-year maintenance interval and want everything in one box
Generac 5664 Air Cooled Home Standby Generator Maintenance Kit is right for you if…
- You own a 13kW to 17kW Generac with a 760/990cc OHVI engine
- Your generator was manufactured between 2008 and 2012
- You only need one spark plug and prefer the chamois cloth for cleanup
❌ Who Should Skip All of These?
If your generator isn’t a Generac air-cooled standby model — or you have a portable generator rather than a permanently installed unit — neither of these kits will fit. You’d be better off looking for a universal maintenance kit or checking your owner’s manual for the correct part numbers.
For the vast majority of homeowners with a Generac standby generator, I’d point you toward the 6485 if you have a 20kW or 22kW model, and the 5664 if you have a 13kW to 17kW model. Get the one that matches your engine size and you’ll be back up and running in under an hour.
Frequently Asked Questions
Will the Generac 6485 kit work on my 17kW generator?
No, the 6485 is specifically designed for 20kW and 22kW generators with the 999cc engine. If you have a 17kW model, you need the Generac 5664 kit instead, which is built for 13kW-17kW generators with 760/990cc engines. Using the wrong kit means you’ll get two spark plugs when you only need one, and the air filter may not fit properly.
Which kit includes more parts — the 6485 or the 5664?
The Generac 6485 includes more components overall. It comes with a pre-cleaner, air filter, oil filter, oil funnel, two spark plugs, a blue cloth, instruction manual, and a reminder sticker. The 5664 includes an air filter, oil filter, oil funnel, one spark plug, a chamois cloth, instruction manual, and a reminder sticker. The 6485 is the more complete kit because it adds the pre-cleaner and an extra spark plug.
Is the Generac 5664 compatible with newer generators?
Only if your generator was made between 2008 and 2012. Generac specifically states the 5664 is designed for air-cooled standby generators from those model years with 760/990cc OHVI engines. If your generator is newer than 2012, I’d double-check the compatibility before buying, or go with the 6485 which fits a wider range of newer 20kW-22kW models.
Do both kits include oil for the oil change?
No, neither kit includes oil. Both the 6485 and the 5664 require you to purchase oil separately. Generac recommends using high-quality oil that matches your generator’s engine specifications. The kits do include an oil funnel, which is a nice touch that makes pouring the oil much less messy.
Which kit is better for a 20kW generator — the 6485 or the 5664?
The 6485 is the clear winner for a 20kW generator. The 5664 is only designed for 13kW-17kW models, so it won’t have the right parts for your 20kW engine. The 6485 is specifically made for 20kW and 22kW generators with 999cc engines, and it includes two spark plugs which your 20kW model requires for proper operation.
How often should I replace the maintenance kit on my Generac generator?
Generac recommends performing maintenance every 200 hours of generator operation or every 2 years, whichever comes first. If your generator runs in a dusty environment, you may need to do it more frequently. Both the 6485 and 5664 kits include a maintenance reminder sticker to help you keep track of when the next service is due.
My Final Verdict
The Generac 6485 is my clear winner here — it’s the more complete kit with two spark plugs, a pre-cleaner, and a blue cloth, all designed for the popular 20kW and 22kW 999cc engines. The 5664 is a solid runner-up if you own a 13kW-17kW model with a 990cc engine, but it only includes one spark plug and lacks the pre-cleaner. For most homeowners with a larger standby generator, the 6485 delivers everything you need in one box.
If you’re still on the fence, check your generator’s model number and engine displacement first. A 999cc engine means you want the 6485; a 990cc engine on a 13kW-17kW model means the 5664 is your match. Either way, you’re getting a genuine Generac kit with a 4.8-star rating and the right parts for a proper tune-up.
Winner: Generac 6485 Scheduled Maintenance Kit
- FITS 20KW, 22KW, 24KW, AND 26KW GENERAC STANDBY GENERATORS: Designed for air-cooled Generac...
- COMPLETE OEM SERVICE KIT WITH ALL REPLACEMENT PARTS INCLUDED: Contains one OEM air filter, one foam...
- GENUINE GENERAC PARTS PROTECT ENGINE LIFE AND WARRANTY COMPLIANCE: Factory-engineered OEM components...
Best for anyone with a 20kW or 22kW 999cc generator who wants the most complete kit with two spark plugs and a pre-cleaner.
Runner-Up: Generac 5664 Air Cooled Home Standby Generator Maintenance Kit
- Comprehensive Maintenance Kit: The Generac 5664 Maintenance Kit is designed specifically for Generac...
- Optimum Performance: With the Generac Guardian Maintenance Kit, you can ensure that your home...
- Complete Contents: This kit includes an air filter, oil filter, oil funnel, spark plug, chamois...
Best for owners of 13kW-17kW 990cc generators made between 2008 and 2012 who need a genuine Generac kit with one spark plug.
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