Zinc ZDDP Oil Additive for Vintage Honda Motorcycles | Rislone Hy-Per Lube
Modern engine oils don't carry the zinc content your air-cooled Honda was designed to run on. Cam lobes and rocker arms — a common fail point on vintage Hondas — are where that shows up first. This ZDDP supplement adds the zinc back. Two ounces per quart of oil at every oil change. One 11 oz bottle covers about two oil changes on a typical twin.
Why You Need This
Modern motor oils lack the metals and minerals old engines need to protect their insides from wear and excessive heat. One of the most important is zinc — a soft metal that acts as a cushion between hard metal parts. Without it, camshaft lobes and rocker arms wear fast, especially on vintage Honda twins and fours where those parts are a known weak point.
Zinc ZDDP (zinc dialkyldithiophosphate) stabilizes modern oil and protects against viscosity breakdown caused by thermal cycles. It reduces friction, especially at startup, which means less wear and a cooler-running engine. It also makes the oil stickier, so it clings to metal parts and cylinder bores instead of draining back to the sump — an important feature for engines that sit through winter storage and cold-start in spring.
We've been recommending Rislone's Hy-Per Lube Zinc ZDDP Supplement for every oil change on every vintage Honda we service — CT90 through CB750 — for years. Two ounces per quart is the dose we use in our own shop and in every one of our model-specific oil change videos.
Specifications
| Spec | Detail |
|---|
| Brand | Rislone Hy-Per Lube Zinc ZDDP Supplement |
| Size | 11 fl oz bottle |
| Active Chemistry | Zinc dialkyldithiophosphate (ZDDP) |
| Recommended Dose | 2 fl oz per US quart of engine oil |
| Typical Coverage | About 2 oil changes on a twin-cylinder Honda; more on singles; less on fours |
| Fits Models | CT90 (1966–1979), CB100 / CL100 / SL100 (1970–1973), CB125 / CL125 / SL125 (1971–1979), CB175 / CL175 / SL175 (1968–1973), CB200 / CL200 (1973–1976), CB350 / CL350 / SL350 (1968–1973), CB350F (1972–1974), CB360 / CL360 / CJ360 (1974–1977), CB400F (1975–1977), CB450 / CL450 (1965–1974), CB500T (1975–1976), CB500K (1971–1973), CB550K / CB550F (1974–1978), CB750 K0–K8 / F0–F3 / A Hondamatic (1969–1978) |
| Sold As | Single 11 oz bottle |
Use with mineral-based 15W-40 diesel truck oil. Honda's factory SAE spec is 10W-40 for most of these engines, and a real 10W-40 motorcycle mineral oil works fine. But we get better results from 15W-40 mineral-based diesel truck oil — the detergent and metal additive package is closer to what these engines were designed to run on. Pair that with 2 oz of ZDDP per quart.
Avoid semi-synthetic and synthetic blend oils. Your Honda has a wet clutch — the clutch plates run in the same oil that lubricates the engine. Friction modifiers in most semi-synthetic oils can cause the clutch friction discs to slip. Shell Rotella T4, Chevron Delo 400, and Mobil Delvac 1300 — all long-time picks for vintage bikes — reformulated to semi-synthetic blends in late 2023. Check the current label before you buy. Look for "100% mineral" or "conventional"; avoid anything marked "synthetic blend" or "semi-synthetic."
Oil Capacity — Reference
Use this table to calculate your additive dose at an oil change. 2 fl oz of additive per US quart of oil.
| Model | Oil Capacity (Refill) | Additive per Change |
|---|
| CT90 / Trail 90 | ~1.0 US quart (0.9 L) | ~2 oz |
| CB350 / CL350 | 2.1 US quarts (2.0 L) | ~4 oz |
| SL350 | 2.3 US quarts (2.2 L) | ~4.5 oz |
| CB360 / CL360 / CJ360 | 1.6 US quarts (1.5 L) | ~3 oz |
| CB450 / CL450 / CB500T | 2.9 US quarts (2.8 L) | ~6 oz |
| CB500K (1971–1973) | 3.2 US quarts (3.0 L) | ~6.5 oz |
| CB550K0–K2 / CB550F | 3.2 US quarts (3.0 L) | ~6.5 oz |
| CB550K3 / K4 (later) | 3.4 US quarts (3.2 L) | ~7 oz |
Capacities above are for refill after a standard oil change with filter service. First-fill dry-engine capacities can differ — consult your owner's manual for those. CT90 figures reflect the OHC engine.
Installation
Difficulty: Beginner.
- Change your engine oil as normal — drain old oil, service the filter, replace the drain plug with a fresh crush washer.
- Calculate your dose: your engine's oil capacity in US quarts × 2 = ounces of additive. Example: a CB360 takes 1.6 quarts × 2 = ~3 oz of additive.
- Pour the measured additive into the crankcase first, then top up with your fresh 15W-40 mineral diesel oil to the correct fill level.
- Run the engine for 2–3 minutes to mix, let it sit overnight, and recheck the oil level in the morning.
Measuring the dose. The bottle has graduated markings on the side. Precision isn't critical — within half an ounce is fine.
Our CB360 oil change video walks through the full procedure including the zinc additive step. We have model-specific oil change videos for CB350 / CL350 / SL350, CB450 / CL450 / CB500T, CB550 / CB500K, and CT90 / Trail 90.
Frequently Asked Questions
The bottle says "not for wet clutch applications." My Honda has a wet clutch. Is this really OK to use?
Every Honda in our fitment list above has a wet clutch. We recommend this additive for all of them, at the 2 fl oz per quart dose, and we use it in our own shop. If you have questions about your specific bike, contact us before your next oil change.
What oil should I use with this?
We recommend a 100% mineral-based 15W-40 diesel truck oil. The classic picks used to be Shell Rotella T4, Chevron Delo 400, and Mobil Delvac 1300, but as of late 2023 those brands reformulated to semi-synthetic blends. Check the current label — look for "100% mineral" or "conventional," avoid "synthetic blend" or "semi-synthetic." A true 10W-40 motorcycle mineral oil also works (Honda's factory SAE spec). See our oil change guides for CT90, CB175 / CL175 / CB200, CB360 / CL360 / CJ360, CB450 / CL450 / CB500T, and CB550 / CB550F / CB500K.
How much should I add?
2 fluid ounces per US quart of engine oil. A CB360 (1.6 quarts) takes about 3 oz. A CB550 (3.2 quarts) takes about 6.5 oz. See the Oil Capacity Reference above for per-model dosing.
How many oil changes does one bottle last?
Depends on your bike. A CB360 stretches a bottle to three changes. A CT90 lasts five or more. A CB550 or CB750 will use more than a bottle per change. Roughly, one 11 oz bottle covers two oil changes on a typical twin.
My bike already uses Honda GN4 or another motorcycle-specific oil. Do I still need this?
Motorcycle-specific oils vary in zinc content. Check the manufacturer's spec sheet. If the oil you're using is mineral-based with high zinc/phosphorus content, you may not need additional ZDDP. If the spec sheet doesn't list specific zinc content, adding 2 oz per quart is the safest bet.
I've been running my bike on modern oil without zinc additive for years. Did I hurt anything?
There's no way to know without pulling the valve cover to look. Going forward, switch to mineral 15W-40 diesel oil and add 2 oz of ZDDP per quart at your next oil change. If you're hearing new top-end noise that wasn't there before, pull the valve cover and inspect the cam lobes and rocker arm tips.
Can I add this to a 2-stroke engine?
No. This is a 4-stroke engine oil additive. 2-stroke engines use pre-mix or oil-injection and don't have a wet sump where a ZDDP additive would live.
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Last updated: April 2026
