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Head-to-head · Best Motor Oil Additives For Motorcycles Under $200

Honda HP4M Additive vs ZDDPlus Engine Oil Additive

Which is the better buy? Side-by-side on rating, price, strengths, and watch-outs — with the published ratings we averaged to get there.

The short answer

Honda HP4M Additive comes out ahead by a narrow margin (4.5 vs 4.3). The gap is mostly about Racing performance enthusiasts — read the strengths below before deciding.

Honda HP4M Additive
Higher ratedRanked #3 in Best Motor Oil Additives For Motorcycles Under $200
Honda HP4M Additive
$29

Honda HP4M is a semi-synthetic blend with molybdenum additives specifically designed for high-heat racing applications. Reviews indicate it provides superior engine protection and can increase horsepower in high-performance scenarios, as noted by Honda's recommendation for TRX450R owners. However, the moly content makes it unsuitable for transmission use, and it's not recommended for casual riders who don't engage in high-stress riding. The oil is formulated for maximum performance in extreme temperatures and reduces oxidation and viscosity loss. This product is best suited for serious performance enthusiasts rather than everyday riders.

Strengths
  • — Contains molybdenum additive for reduced friction and heat in high-temperature situations
  • — Formulated for high heat, 4-stroke motorcycle racing applications
  • — Provides superior engine protection as recommended by Honda for TRX450R
Watch-outs
  • — Not recommended for transmission use due to molybdenum content
  • — Designed for high-performance riding only, not suitable for normal daily use
  • — May not be necessary for casual riders who don't operate near redline
Full review →
ZDDPlus Engine Oil Additive
Ranked #2 in Best Motor Oil Additives For Motorcycles Under $200
ZDDPlus Engine Oil Additive
$18

ZDDPlus Engine Oil Additive is designed specifically for classic and performance engines with flat-tappet camshafts, restoring the ZDDP levels that were removed from modern SM-rated oils to protect catalytic converters. According to rjcracing.com, it's a concentrated solution that can be added to any oil type and has been tested against other additives. However, Tom's Hardware-style reviewers note that it's only beneficial for pre-1990s engines, as modern vehicles with OBD II systems and roller lifters don't require this additive. The product is priced at $18.95 per bottle and must be shipped ground due to shipping restrictions. This additive fits best for owners of classic muscle cars, trucks, and high-performance vehicles with flat-tappet cams, but should be avoided by owners of modern vehicles.

Strengths
  • — Restores ZDDP levels to 'SF' category oil standards for older engines with flat-tappet cams
  • — Compatible with both synthetic and conventional oils, mixes easily with existing oil
  • — One 4-oz bottle per oil change provides sufficient ZDDP for classic and performance engines
Watch-outs
  • — Only suitable for pre-OBD II vehicles with flat-tappet camshafts, not recommended for modern vehicles
  • — Must be shipped via ground UPS, cannot be sent via USPS or air freight
Full review →

How they stack up

Honda HP4M Additive

Honda HP4M's molybdenum additives provide superior protection in high-heat racing conditions, unlike Lucas Oil Stabilizer which is more general-purpose for worn engines. While Bel-Ray Friction Modifier reduces fluid friction, Honda HP4M is specifically formulated for racing applications and provides better oxidation resistance than Liqui Moly's fuel system cleaning, making it ideal for extreme performance scenarios rather than everyday use.

ZDDPlus Engine Oil Additive

ZDDPlus is specifically designed for flat-tappet camshafts, unlike Lucas Oil Stabilizer which works on all high-mileage engines, making it more niche but essential for classic vehicles. While Bel-Ray Friction Modifier targets friction reduction in motorcycles, ZDDPlus focuses on restoring ZDDP levels in older engines, and unlike Honda HP4M, it's not formulated for racing applications but rather for protecting flat-tappet camshafts in pre-OBD II vehicles.

Specs side-by-side

SpecHonda HP4M AdditiveZDDPlus Engine Oil Additive
FormulationSynthetic/mineral blendZinc DialkylDithioPhosphate (ZDDP)
Viscosity10W-40—
Volume1 Quart4 oz
CompatibilityHonda scooters (PCX, Forza)All high-quality oils (synthetic or conventional)
Key BenefitsFriction-reducing molybdenum, fuel economy, peak horsepowerRestores ZDDP levels, protects flat-tappet cams
Additive TypeMolybdenumZinc ZDDP Supplement
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